Error "invalid_grant" Apex SDK

Affected: Apex server-side SDK

Symptoms

Both of the following error occurs when running the bridge:

Salesforce auth failure: 400{"error":"invalid_grant","error_description":"authentication failure"}<nil>
Error running bridge: {"error":"invalid_grant","error_description":"authentication failure"}

Cause

Either the OAuth 2.0 Username-Password flow is blocked, or the OAUTH_USERNAME or OAUTH_PASSWORD environment variables are invalid.

Solution

1. Ensure that the Allow OAuth Username-Password Flows option is enabled.  
2. Double-check that the OAUTH_USERNAME and OAUTH_PASSWORD environment variables are correct.