Recipient not receiving AirTag sharing invite

I have an AirTag I am trying to share with a Family member.

When I try to Share the AirTag with them, I believe they are supposed to receive a notification or invite within their Find My app.

However, they have not received that invite, and do not see the AirTag.

If it means much, I'm on iOS26, they are on iOS18.

Is this a known issue? Is there a known fix?