WebSphere Docker OAuth
Would you be able to turn on and provide the server trace for that invocation? The message indicates that either credentials weren't found in the request, or credentials were found but were invalid for that client. It would be useful to know which is the case here.
You can enable trace by adding this snippet to your server.xml:
<logging traceSpecification="*=info=enabled:com.ibm.ws.security.*=all=enabled:com.ibm.oauth.*=all=enabled" />