[URGENT] Cloud instance 431 Error on Gmail Custom OAuth2 - Backend Session Reset Needed

Questions
1

Hello,
My production workflow is completely blocked due to a persistent “HTTP Status Code 431 (Request Header Fields Too Large)” error on my n8n Cloud instance.
This happens on the oauth.n8n.cloud proxy side immediately when clicking “Sign in with Google” using Gmail Custom OAuth2. I have already fully cleared my browser cache, tried completely different clean browsers, and rebuilt the credentials from scratch. The issue persists.
An AI support ticket has been created, but I urgently need a human developer to manually reset the OAuth state/session cache for my instance on the backend.
Instance URL: santino.app.n8n.cloud

Describe the problem/error/question

What is the error message (if any)?

Please share your workflow

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Share the output returned by the last node

Information on your n8n setup

  • n8n version:
  • Database (default: SQLite):
  • n8n EXECUTIONS_PROCESS setting (default: own, main):
  • Running n8n via (Docker, npm, n8n cloud, desktop app):
  • Operating system:
2

Have tried the InCognito mode? You can also reset the browser → Reset settings from Settings menu.

Then delete the Credentials from the workflow and re-add it.

3

@Jon_James , can you help?

4

Hey

There’s an active support thread for this, one of the team is looking in to it.