I am trying to move users from OCS to Lync 2013 from within the Lync 2013 Control Panel and am getting an error that states "Cannot find Registrar pool. Verify that "FQDN of old pool" is a valid registrar pool.

Give this Lync powershell command a go:

Move-CsLegacyUser <user> -Target <Lync2013 Pool Name>

Move-CsLegacyUser -Identity "Pilar Ackerman" -Target "atl-cs-001.litwareinc.com"

Have you reviewed the OCS to 2013 migration documents?

http://technet.microsoft.com/en-us/library/jj205375.aspx

Did you add the OCS pool to the 2013 topology?

Hi,Debi Scott,

Do you have DNS record for the old OCS pool?Could you pease verify that you can ping the FQDN of the old pool from Lync 2013 server?

Regards,

Sharon

Looks like the issue was with the merge of the OCS topology with the Lync topology. It is resolved now. It had to do with the incorrect name of the old pool during the merge.

Thanks