SSO Error prior Control Center Login

Hello,

after registering vRO Appliance to vSphere SSO login to Control Center is not possible.

-> PSC URL is displayed with Error 500 prior login

-> in PSC Logs we can see this error:

[2017-10-24T09:28:09.703+02:00 vsphere.local aa8544fb-f398-4acd-a7ba-fdfc5cfc4463 ERROR] [ServerUtils] Exception 'com.vmware.identity.idm.IDMLoginException: Login failed'

-> vRO is newly installed

-> Single PSC   

-> vRO 7.30

-> PSC 6.0 U2

Any hints?

Best Regards,

Markus