3169247 - "No OAuth 2.0 client authentication credentials included or used authentication method is unsupported" error when terminating the access token request in plain HTTP

While making use of an OAuth-based access token request on the NetWeaver AS ABAP environment, a manual user name and password prompt occurs as the below error message is recorded:

"OAUTH2: Error! CX_OAUTH2_EXCEPTION thrown, time: ...

OAUTH2: Error Text: No OAuth 2.0 client authentication credentials included or used authentication method is unsupported"

• NetWeaver AS ABAP.
• Proxy, load balancer or web dispatcher may be intermediating the connection.

OAuth, HTTP, HTTPS, invalid_request, OAUTH2, authentication, credentials, method, unsupported , KBA , BC-SEC-LGN-OA2 , OAuth 2.0 for ABAP , Problem