Airtag sharing option not showing

I am trying to share an AirTag from my sons phone, but cannot see the option to share once the tag is added to my sons phone. If I remove the tag from my sons phone and add it to my account, I can share the AirTag with him, but he never gets a notification to add it, and it doesn't show up in Find My (on my Find My it just shows as 'Pending'). If I share the AirTag with my wife, she gets the notification from me and can add it.

So the problem seems to be with my sons phone.

All phones are on ISO 17.0.3 and are an iPhone 15 Pro Max, an iPhone 15 and an iPhone 13.

I have tried all of the solutions mentioned for similar problems in these forums (removing the AirTag and adding it again, when sharing with my son from my phone adding his number instead of selecting him from Contacts, removing the battery from the AirTag and trying again) but it won't share with my son and my son cannot see the share option when the AirTag is assigned to him.

One member on these forums who had a very similar issue (trying to share with his son) said his son had Content and Privacy Restrictions on, and when he turned these off he could share with his son. My son also has Content and Privacy Restrictions turned on, but even after turning these off (and rebooting his phone) the option to share is not there, and if I add the AirTag to my phone and share it with him, he never receives the invite.

My gut feeling is its something to do with the Content and Privacy Restrictions (as I can share the AirTag with my wife with no issues at all) - but am not sure what else I can do. They have been switched off completely.

Can anyone please advise ?