Adprep could not contact the Schema FSMO %1. The Schema FSMO must be reachable for this operation to proceed. Status/Consequence ...

Adprep could not contact the Schema FSMO %1. The Schema FSMO must be reachable for this operation to proceed. 
[Status/Consequence]
The Active Directory Domain Services schema is not upgraded.
[User Action]
Check the log file ADPrep.log in the %2 directory for possible cause of failure.