Calendar items don't sync with Outlook 2007 on Windows

I've synced my iphone countless times with Outlook via iTunes and a cable. Suddenly today, I've found that items I've recently added to my iphone calendar don't get added to my Outlook calendar.

I did a test where I added an item to Outlook, ran a sync, the item was added to my iphone; I then deleted it from iphone, synced again, and it deleted from Outlook - so it seems everything is in place to sync both directions. But, if I add an item to iphone first, it doesn't sync to Outlook.

I've restarted the iphone and the PC. The iphone is on iOS 16.4.1. I know 16.5 just came out, I haven't installed it yet, but I'm only back one version. The PC is still on Win7 - but again, I've done this countless times without a problem. Contacts seem to be syncing fine.

What am I missing???