3492463 - OAuth 2.0 is not supported for External API (Custom CDS view) but it is ticked in "Supported Inbound Authentication Methods" of Communication Arrangement - SAP S/4HANA Cloud Public Edition

You're creating a Communication Arrangement to your External API (Custom CDS View), configuring the OAuth 2.0 but the authentication is not working.

OAuth 2.0 is ticked as supported method in "Supported Inbound Authentication Methods" of created Communication Arrangement.

SAP S/4HANA Cloud Public Edition

External API do not support OAuth 2.0.
Only Basic Authentication is allowed, which is User ID and Password.

The reason why the OAuth 2.0 is ticked as supported is because currently, the Custom Communication Scenario sets all supported authentication methods to available due to the possibility that different services can support different authentication methods. It is not dynamically calculated what methods are supported in the end.

To complete the configuration of your External API, you'll need to use the Basic Authentication.

You can check the documentation SAP Help Portal | External API: Creating a Communication Arrangement which provides step-by-step. 

SAP Help Portal - External API: Exposing a Custom CDS View as OData API

OAuth 2.0, external API, custom CDS view, Supported Inbound Authentication Methods, communication arrangement , KBA , BC-SRV-APS-COM , Maintain Communication System and Arrangement , BC-SRV-APS-GKE , Generic CDS Key User Editor , Problem