Series 7 - some apps won't sync?

I just bought a new iWatch Series 7 (45 mm GPS+Cellular). T-Mobile. iPhone 12 Pro. Everything is updated to latest iOS/OS versions.

The watch did its initial sync and later I also added/changed some faces and those sync'd as well.

Perhaps this is app specific, but the one in question so far is the Fly Delta app (Delta airlines). On the watch it says: "Please open Fly Dleta on your ihone to sync the latest information to your watch."

OK, so I do that. Nothing happens. App opens on iPhone, refreshes the Delta Airlines info and that's it. Watch does nothing. Still continues to say to open it on the iPhone to sync the info.

I've even restarted the iWatch as well.

It DOES show connected to the phone. I can see updated iMessages.

Any ideas?