Here's a post with the various options for repladmin command, and the explanation for each.
Check for errors in replication and fix them first for best results
Exchange 2016 error in a migrated windows server setup
After doing a migration from Window 2008 to Windows Server 2016, and transferring FSMO roles and everything went smoothly, however the problem comes when installing Exchange 2016 on Server 2016, i get an error straight away on step 1. "Organization Preparation" In log file the error is:
"The server side error is: 0x21a2 The FSMO role ownership could not be verified because its directory partition has not replicated successfully with at least one replication partner."
I resolved this by demoting old box (VM), but that sounds more of a "nuclear option" when the real issue is replication error..
How can i check replication is a success? Would DCDIAG show this or would i have to run Repadmin /replsummary