There are scenarios where RevRec sync would have paused on the RS side. This can be easily identified by checking the rev_rec_requests table on the RS side. 

Check the current_sync_status of rev_rec_request, the status would be in SYNC_PAUSED status. 

 

If the status seems to be PAUSED, then check the datasource_settings table. Check if RevLock Integration is set to True here, which means, the customer is using RevLock and hence, the system does not allow the Rev_rec_sync to continue. 

This has to be taken with TAM / CSM of this account and should be confirmed why does the customer want the RS Rev rec when they are currently using RevLock.