I had an issue with a SQL Server directly after creation the protection group.
“Unable to configure protection SQL 2012”.
Unfortunateley the error id 30184 leads to a page without any further Content.
I already protect a lot of SQL Servers since the initial 2012 Release Cycle but this never happend before.
After putting the NT Local System Account to the sysadmin Server role of the SQL Server (2012 SP1) as mentioned here it works and the DPM could get the databases.
It seems to be a misconfigured SQL Server. Some other SQL Servers have these server roles.