Describe the problem/error/question
Hello everyone,
I’m encountering a persistent issue when trying to connect n8n to Google Document AI, despite numerous troubleshooting attempts. I’m reaching out to the community for any help or suggestions.
I’m trying to integrate Google Document AI into an n8n workflow using a Service Account. The initial connection test for the service account in n8n always succeeds: n8n indicates that the connection is “OK”.
However, as soon as I execute the workflow and the “Google Document AI - Structure” node attempts to process a document, I get an authorization error. I have meticulously checked the IAM roles for the service account, enabled the Document AI API, and ensured that the JSON key file for the service account is correctly pasted and unaltered.
My service account ( @.iam.gserviceaccount.com ) has the following IAM roles:
- Document AI Administrator (beta)
- Document AI API User (beta)
- Document AI Editor (beta)
- Document AI Viewer (beta)
- Storage Object Admin (for Google Cloud Storage access).
Despite these seemingly adequate roles, the error persists and points to an issue with the authentication token itself.
The key point is ACCESS_TOKEN_TYPE_UNSUPPORTED , which suggests that the type of OAuth 2.0 access token being generated is not what the Document AI API expects, even though the service account credentials are initially accepted by n8n.
I tried multiple hints from Gemini or n8n AI. All failed. I added scopes, regenerated my JSON, still get an initial connection “SUCCESS”.
Hope someone can help me - Thank you!!
What is the error message (if any)?
Authorization failed - please check your credentials
Request had invalid authentication credentials. Expected OAuth 2 access token, login cookie or other valid authentication credential. See Integrating Google Sign-In into your web app | Web guides | Google for Developers .
Error details
From HTTP Request
Error code
401
Full message
401 - “{\n “error”: {\n “code”: 401,\n “message”: “Request had invalid authentication credentials. Expected OAuth 2 access token, login cookie or other valid authentication credential. See https://developers.google.com/identity/sign-in/web/devconsole-project.\\”,\\n “status”: “UNAUTHENTICATED”,\n “details”: [\n {\n “@type”: “type.googleapis.com/google.rpc.ErrorInfo”,\n “reason”: “ACCESS_TOKEN_TYPE_UNSUPPORTED”,\n “metadata”: {\n “service”: “documentai.googleapis.com”,\n “method”: “google.cloud.documentai.v1.DocumentProcessorService.ProcessDocument”\n }\n }\n ]\n }\n}\n”
{
“headers”: {
“accept”: “application/json,text/html,application/xhtml+xml,application/xml,text/;q=0.9, image/;q=0.8, /;q=0.7”
},
“method”: “POST”,
“uri”: “https://hidden-documentai.googleapis.com/v1/projects/Hidden/locations/hidden/processors/Hidden:process”,
“gzip”: true,
“rejectUnauthorized”: true,
“followRedirect”: true,
“resolveWithFullResponse”: true,
“sendCredentialsOnCrossOriginRedirect”: false,
“followAllRedirects”: true,
“timeout”: 300000,
“encoding”: null,
“json”: false,
“useStream”: true
}
Please share your workflow
Share the output returned by the last node
last node is only a PDF import using postman
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: