Forms API v3 returns 404 ("Form can't be found") despite correct Portal ID and Form GUID in EU regio

Marketing & Content Hub
1

Hi everyone,

I’m trying to submit form data to HubSpot using the Forms API v3 integration endpoint, but I keep getting a 404 error: {"status":"error","message":"Form with guid '6304125e-cd83-4a0c-8567-e849c4e16a64' can't be found"}

Here are my details:

  • Data Center / Region: EU (api-eu1.hsforms.com)

  • Form GUID: 6304125e-cd83-4a0c-8567-e849c4e16a64

  • Endpoint used: [https://api-eu1.hsforms.com/submissions/v3/integration/submit/149093499/6304125e-cd83-4a0c-8567-e849c4e16a64](https://api-eu1.hsforms.com/submissions/v3/integration/submit/149093499/6304125e-cd83-4a0c-8567-e849c4e16a64)

The form exists in our portal under Marketing > Forms, and I copied the GUID directly from the embed code. However, the API still throws a 404.

Are there any specific visibility settings, form types (e.g., legacy vs. standard), or permission requirements for an unauthenticated API submission in the EU region that could cause this?

Thanks in advance for any help!

3

Hey! A few things worth checking here:

The EU endpoint looks correct, but double-check that the form isn’t a legacy form — older form types sometimes don’t play nicely with the v3 submissions endpoint and may need the v2 endpoint instead.

Also worth verifying the GUID directly via the Forms API GET endpoint to confirm it’s returning that exact form for your portal — occasionally the GUID in the embed code doesn’t match what the API expects.

Tagging in a few folks who may be able to help: @matt_scott @Gonzalo @Mike_Eastwood

If none of that resolves it, it’s worth opening a ticket with HubSpot Support since EU data residency portals occasionally have region-specific quirks with form submissions.

Cassie, Community Manager

5

Hi @Borman158

Is your Form a Legacy Form or the new Form (which has multi-step forms and other features).

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If your Form used the Form Editor, not the Legacy Form Editor, the API will not access your form. The API can ONLY access the Legacy Form Type.

I recently had to recreate all of my forms in the Legacy Form Editor to get around this.

Hopefully someone has a workaround.
Mike

6

A huge thank you to the HubSpot community for the help with yesterday’s API puzzle! :raising_hands:

Special thanks for the insights regarding Legacy forms and verifying form GUIDs directly via endpoints — it really helped get to the bottom of those API limitations.

How we ultimately bypassed the issue:

Instead of fighting with legacy editors and direct frontend calls to the HubSpot Forms API, we completely re-architected the flow.

Now, the architecture looks like this:

  1. Frontend (React/Vite) sends form data directly to Supabase (database) for reliable lead storage.

  2. The data is then instantly picked up via Make (Webhooks).

  3. Make automatically dispatches email notifications and handles creating or updating the contact inside HubSpot CRM.

As a result, we completely removed our dependency on HubSpot’s frontend form limitations, made the system robust, and eliminated potential technical debt. Thanks again to everyone who chimed in and shared their expertise! :rocket: