Cannot connect from DC Slave MS Server 2012 R2 to UCS Master after AD Takeover


the primary DC was joined into the UCS Master via AD Takeover.
AD entries in DNS created, so existing win + linux clients can connect without changes and new clients can join to the UCS (AD) without problems.

In the inital DC config some secondary DC´s exists. One of them should now be included in the UCS AD domain also as a backup DC (there is running a special win prog).

Starting this MS DC is no problem, because all DNS entries are copied to the UCS Master DNS.
In Tab “Server Manager” I added the UCS Master but I couldn´t connect to the UCS Master.
Error msg is “no access to the destination server”.

Any idears ?