API [Authentication] - invalid_client

When going through the OAuth2 authentication flow, an "invalid_client" error is returned after the user clicks "Grant Access".

Environment

Custom Applications with users going through the OAuth2 authentication flow.

Steps To Resolve

1. Ensure the parameters explicitly match what is documented in the Authorize user API endpoint documentation. It's not uncommon to miss a letter or number in the parameter values used.
2. If you are still experiencing errors try using only the required API call request parameters (client_id, response_type).

Root Cause

The most common cause is invalid parameter or parameter values being used. Please ensure the parameters explicitly match what is documented in the Authorize user API endpoint documentation, the OAuth 2.0 with SDKs guide, or OAuth 2.0 without SDKs guide.