Adprep could not contact the Domain Naming FSMO to read the partitions. The Domain Naming FSMO must be reachable for this ...

Adprep could not contact the Domain Naming FSMO to read the partitions. The Domain Naming FSMO must be reachable for this operation to proceed. 
[Status/Consequence]
The Active Directory Domain Services DNS partitions are not prepared for Read Only DCs.
[User Action]
Check the log file ADPrep.log in the %1 directory for possible cause of failure.