Apple watch not syncing contacts through family sharing

I saw this question asked in December 2023 with no responses and am wondering if anyone has had any luck as I have spoken with Apple support via phone and spent an hour in the store with no resolution. I set up an Apple watch for my son via Family Sharing one year ago. He has his own iCloud account. Since an update a couple of months ago, we have had issues with updating contacts on his watch and his icloud account. I can update his contact list with my phone in the watch app just fine but the contacts are not synced with his iCloud account or the watch. He also cannot add contacts on his own via the watch - there is no option to do so. The watch is signed in and shows up and respond to Find My. I've reset, restarted, turned contact syncing off and on on the watch, unpaired and repaired the watch, uninstalled and reinstalled the app, all on my own AND with apple tech support and nothing has changed this. It doesn't seem iCloud is connecting properly with contacts. Yet, authorizations and backups appear to be working just fine. Can anyone please help?!