In some cases you might experience a connection issue to the CMIS attached FileNet P8 object stores. In the WebSphere SystemOut.log of you CMIS server you will see this error:
com.filenet.api.exception.EngineRuntimeException: FNRCS0005E: SECURITY_INVALID_CREDENTIALS: Access to the Content Engine was not allowed because the Content Engine API library or the Web Service Interface (WSI) Listener could not find the required security context information. Expected credentials were not found in the security context
When you try the same with EJB it is working fine. So to solve the issue and use WSI instead of EJB you need to add two JAVA parameters to the JVM of you application servers.
The following JVM parameter must be set on the application server running Content Platform Engine
-Dcom.filenet.authentication.token.userid=sso:ltpa
The following JVM parameter must be set on the application server running CMIS
-DFileNet.WSI.AutoDetectLTPAToken=true
Now restart both CPE and CMIS server and try to connect via WSI again.