AD Sync Error

I'm currently running ASGRD15 and demoing 2017. I'm trying to set up a sync from a specific OU in Active Directory in a new folder. I've specified the OU and domain admin credentials to use to scan the OU, but when I attempt the sync I get an error, "Error reading from active directory. Sync aborted. Object reference not set to an instance of an object." 

I did some poking around on the error, but no luck figuring out why I'm getting it.

--Tom