Non-admin users cannot retrieve OAuth token from OAuth Credentials table to make outbound REST call.
This is because of ACLs on OAuth Credentials table which mandate that the user should have been the one who initially created the token or should be an admin user to read the token.
To fix the issue you will need to create 2 new ACLs and make sure non-admin users pass these ACLs.
- Table level"read" ACL on oauth_credential
- Field level "read" ACL on "oauth_credential.token_received"