A Developer’s Guide to Solving HubSpot CMS Errors

Working with HubSpot CMS can be smooth, until it isn’t. One small change in your custom module or theme, and suddenly, things stop behaving the way they should.

Developers often assume they’ve made a big mistake. But in most cases, it’s something minor. A missing tag. A wrong file path. A tiny syntax error in HubL that doesn’t throw any warning.

And unlike other platforms, HubSpot won’t always show you what went wrong. No loud errors. Just quiet failures.

If you’re building templates, custom modules, or working with HubDB or APIs, you’ll likely face these issues at some point. And when that happens, it helps to know where to look.

This blog is not theory. It’s a collection of real development errors in HubSpot and how to solve them without wasting hours chasing the cause.

Common HubSpot CMS errors and how to fix them

1. Common Troubleshooting Steps Before You Panic

Not every HubSpot development issue needs deep debugging. Often, the fix is simple. Below is a list of basic checks you should perform before assuming your code is broken:

Check your internet connection

• Problem: HubSpot’s editor may not save or sync changes if your connection drops.
• Fix: Refresh the page. Make sure you’re online and your changes are actually saved.
  

Clear your browser cache

• Problem: Your browser may be loading an old version of your layout or module.
• Fix: Clear cache or use incognito mode. Then recheck the changes.
  

Verify if the template/module is published

• Problem: Draft files won’t reflect on the live site or even in preview mode.
• Fix: Go to the Design Manager and make sure everything is published, not just saved.

Check the console in developer tools

• Problem: Some JavaScript or HubL errors appear quietly in the browser’s console.
• Fix: Open developer tools (F12), go to the Console tab, and look for red or warning messages.
  

Check your user permissions

• Problem: Limited access may block editing or publishing certain templates or files.
• Fix: Ask the portal admin to grant you full access, especially if you’re working in a client account.
  

These basic steps help catch common mistakes. Always run through them before digging into code or calling support.

2. Changes Not Being Saved in the Editor

While working in the HubSpot content editor, you might get a warning that your changes aren’t being saved. This alert usually shows up when the same page or blog is open in multiple tabs or browsers. The editor stops saving to prevent content conflicts.

How to fix it

• Click “Go back to editor” to return safely
• Copy your unsaved changes to avoid losing them
• Close any duplicate tabs or browser windows
• Reload the editor to fetch the latest saved version
• Paste your copied content and click Save
• If the problem keeps happening, clear your browser’s cache or switch to another browser
  

To avoid this, stick to editing one page at a time on a single tab.

3. HubSpot API Authentication Error (401 or 403)

When trying to connect with HubSpot’s API, you may get a 401 Unauthorized or 403 Forbidden error. This usually blocks your integration or script from working as expected.

These errors are frustrating because they often appear even when your code seems fine. But the issue is almost always related to access problems.

Why it happens

• The access token is expired or incorrect
• The token does not have permission for the requested scope
• The private app was deleted or disconnected from the portal
• Headers are missing or incorrectly formatted
• You’re using an API key, which is no longer supported
  

How to fix it

• Double-check your access token. Generate a fresh one if needed
• Ensure the app has the correct scopes enabled for the API you’re calling
• Confirm that the app is still connected to your HubSpot portal
• Always include the Authorization header: “Authorization: Bearer YOUR_ACCESS_TOKEN”
• Use a tool like Postman to test the request and debug the response
• Avoid using old API keys. Move to private apps with OAuth or token-based auth
  

When troubleshooting API issues, always start by checking the token and scopes. Most problems are solved there.

4. Content Won’t Load on a Specific Network

You visit a HubSpot-hosted website, but the page doesn’t load. It keeps spinning or times out. Strangely, others can access it just fine. You test it on your mobile with Wi-Fi off, and it opens instantly. This tells you the issue is not with the site itself but with the network you’re using.

Why it happens

This usually happens when the internal network blocks or misroutes DNS requests due to outdated CNAME records, cached entries, or firewall rules that restrict access to HubSpot domains.

How to fix it

• Switch to mobile data or another Wi-Fi network to confirm it’s a network-based problem
• Ask your IT team to flush the DNS cache on the local network
• Make sure the DNS configuration in the internal network matches what HubSpot provides
• Verify that the correct CNAME records are set in the internal DNS
• Check firewall or content filter settings that might block HubSpot domains
• If you’re using a custom domain, confirm it’s pointing to HubSpot’s correct records
  

DNS issues are tricky because they don’t always break everything. Sometimes, they block just one page or domain. That’s why testing on a separate connection helps rule things out fast.

5. CSS or JavaScript Not Loading

Your page loads, but everything looks plain. No colors, no layout, no scripts running. Buttons stop working. Carousels won’t slide. This usually means your CSS or JavaScript files are either not loading or have failed silently in the background.

This is a common issue after uploading custom files or switching templates.

How to fix it

• Double-check the file paths for your CSS and JS files
• If using CLI, run hs upload to push local changes to the portal
• Use HubL’s {{ require_css }} and {{ require_js }} inside your modules or layouts
• Check the browser’s Network tab to see if any files are blocked or failed to load
• View the Console tab to catch syntax errors in JavaScript
• Ensure any third-party scripts (like jQuery or Swiper) are loaded before your custom scripts
• Try testing in incognito mode to bypass cached resources
  

Always preview your page after uploading files, and verify each resource is loading properly. A broken link or one missing tag is often all it takes to break the layout.

6. Template Updates Aren’t Reflected in Existing Content

You’ve made updates to your template, but the changes don’t show up on existing pages. Everything looks exactly the same, even after saving and publishing.

Why it happens

HubSpot only pushes changes to locked modules and global modules. Any edits made to unlocked or custom content will not update existing pages automatically.

How to fix it

• In Design Manager, right-click the module and select “Prevent editing in content editors.”
• Publish the template after locking the module
• For global modules, changes should apply across all pages
• If updates still don’t reflect, try making a small edit (like adding a space) and publishing again
• This forces a re-render, which often resolves the issue
  

To keep future content consistent, it’s better to use locked or global modules for sections you don’t want editors to modify.

7. Troubleshooting Data Sync Issues

When HubSpot fails to sync with external tools or CRMs, the result is often missing data, outdated records, or broken workflows. These problems can quietly affect reports, emails, and task automation.

Why it happens

• Field mappings don’t align properly
• Duplicate records are causing conflicts
• API rate limits are exceeded during bulk sync
• Unstable internet interrupts data transfer
  

How to fix it

• Open the integration settings and review field mappings one by one
• Match data types between systems and make sure all required fields are connected
• Use HubSpot’s Manage Duplicates tool to clean up any conflicting records
• Check your API usage under the developer settings. Space out sync jobs or request a higher limit if needed
• Monitor the sync status and logs from HubSpot’s integration page to spot failed records
• Use a reliable internet connection while syncing large volumes of data to avoid timeout or partial updates

8. Troubleshooting Email and Marketing Automation Issues

Emails aren’t reaching users. Workflows stop midway. Lists are missing key contacts. These issues can quietly damage your campaigns if not resolved quickly.

Why it happens

• Emails are marked as spam or bounce due to invalid addresses
• Your sending domain lacks authentication, reducing trust
• Workflow triggers are set up incorrectly or are missing
• Segmentation filters don’t match the intended audience
• Some lists are outdated and no longer updated automatically
  

How to fix it

• Check your email sending domain. Make sure SPF, DKIM, and DMARC are configured properly
• Clean your contact list regularly to remove invalid or inactive addresses
• Open your workflows and test each trigger to confirm the logic is correct
• Fix errors in workflow steps that cause them to pause or fail
• Review smart list filters to make sure they reflect the right criteria
• Monitor engagement reports and remove users who consistently don’t interact with your emails

Final Take

Most HubSpot development errors aren’t complex, but they do waste time when left unchecked. From broken layouts to API failures, the smallest misstep can affect the entire site.

If you don’t want to deal with these kinds of problems, it’s better to have a reliable team behind your setup. Mistakes in templates or automation can quietly hurt performance over time.

At Stellites.com, our developers can help you build your website from the ground up or handle ongoing maintenance. Whether you need custom modules or monthly support, we’re here to keep your site running smoothly.

FAQs

1. What should I check first when a HubSpot page breaks after a theme update?

Start with the module structure. Recheck require_css or require_js usage, and clear your browser cache. Even a missing comma in HubL can silently break the whole page.

2. Can multiple developers work in the HubSpot Design Manager at once?

Yes, but avoid editing the same file in different tabs. It may trigger version conflicts or overwrite unsaved changes. Use Git + CLI for better collaboration control.

3. Why do template changes not apply to older pages in HubSpot?

Because non-global or unlocked modules do not auto-update. Use global modules or lock modules in templates if you want consistent updates across all pages without manual edits.

4. How do I make sure my HubSpot forms work on every network?

Test forms on mobile data and different browsers. If they don’t load on specific Wi-Fi networks, check DNS settings or firewall rules blocking HubSpot’s assets or endpoints.

5. Can I avoid these HubSpot errors without hiring a full-time developer?

Absolutely. At Stellites.com, our expert developers can build or maintain your HubSpot website without long-term hiring. Whether it’s a one-time fix or ongoing help, we’ve got you covered.