Contact photos not synching across all devices

Good day - I have an issue with contact photos not synching to all of the devices in the account -

Here's a rundown of the devices - bold indicates to me that things aren't as they should be.

2011 iMac running High Sierra 10.13.6 - photos show in Contacts, unable to logon to Messages app.

2017 iMac running Big Sur 11.3.1 - photos show in Contacts and in Messages

2011 MacBook Pro 13 inch running High Sierra 10.13.6 - photos show in Contacts and in Messages

2017 MacBook Air 13 inch running Big Sur 11.3.1 - photos show in Contacts and in Messages

2nd generation iPad Pro 12.9 running iOS 14.6 - no contact photos in Contacts or in Messages app. 'Show Contact Photos' is selected in Messages preferences in Settings.

iPhone 7 Plus running iOS 14.6 - photos show in Contacts and in Messages app

Additionally - when I logon to iCloud.com and view my account - when I look at 'Contacts' there are no contact photos. When I try to edit the contact photo I get a popup message that says 'Your photo could not be loaded at this time. Try again later.'

Also when I check Settings in iCloud.com the 2011 iMac does not show up as one of 'My Devices'. It does show up in my list for Find My iPhone - it can be located, and plays a sound when commanded to by Find My iPhone.

All contacts synch, and all calendar items synch as they should.

I'm considering restoring the iPad, calling it a new device, setting it up and then adding back the apps that are currently loaded on it. I'm concerned that if after I set it up as a new device, and getting the Contacts/Messages working correctly, that if I restore it from a backup that the problems will re-emerge. Ditto for the 2011 iMac -

iCloud is also configured to be used by Contacts and Messages.

Any ideas appreciated -