The user "MYUSER" does not exist in the database

Running RTC 3.0 on iSeries V5R4 I always get user "ADMIN" when logging into https://as4edcdevl:29443/jts

Even when using the credentials of a newly created user, it keeps on displaying "ADMIN" in the upper right corner ?

In the WAS logs I also see...

Caused by: net.oauth.OAuthException: The user "MYUSER" does not exist in the database
at com.ibm.team.repository.service.internal.oauth.OAuthServiceProvider.runAsUser(OAuthServiceProvider.java:1163)
at com.ibm.team.repository.service.internal.oauth.OAuthServiceProvider.getKeyAndSecret(OAuthServiceProvider.java:1202)
at sun.reflect.GeneratedMethodAccessor109.invoke(Unknown Source)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at java.lang.reflect.Method.invoke(Method.java:618)
at org.eclipse.soda.sat.core.internal.record.ExportProxyServiceRecord.invoke(ExportProxyServiceRecord.java:370)
at org.eclipse.soda.sat.core.internal.record.ExportProxyServiceRecord.access$0(ExportProxyServiceRecord.java:356)
at org.eclipse.soda.sat.core.internal.record.ExportProxyServiceRecord$ExportedServiceInvocationHandler.invoke(ExportProxyServiceRecord.java:56)
at $Proxy233.getKeyAndSecret(Unknown Source)
at net.jazz.ajax.service.internal.http.ThemingHandler.sendLocalRequest(ThemingHandler.java:1480)
... 33 more

Even when logging in with RTCADM I get the same message in my joblog. In addition to the above stacktrace, I also get other stacktraces regarding the "The user ... does not exist in the database".