iTunes -> iPhone Photos won't sync

We're old school and use iTunes to sync (not iCloud) for Photos. We have two iPhones, both 6’s and both running the same IOS version.  One syncs photos just fine, the other doesn’t.  I have only one album set to sync to the phone, it is not new, so has synced in the past. Recently, the sync process on ITunes completes reading the Photos library much too fast, faster than when syncing another IPhone that doesn’t have this problem. Unfortunately, the photos don't sync. Details below.

IPhone 6 running IOS 12.2

2009 IMac running MacOS 10.12.6

ITunes 12.8.2.3

Thanks!