Mac Messages app - screen sharing icon disabled - why?

Hi all, I am trying to screenshare with my dad to fix several issues with his Mac after he updated to Catalina. However the screen sharing icon is always disabled. We tried turning off screen sharing in system preferences, rebooting the machine and turning it back on again. It stays disabled.
Is there some other hidden setting that needs to be enabled (Firewall?) to enable screen share through messages?

Now that I hung up on the hour + Facetime call, that we conducted via his iPad and my Mac, I’m wondering if that blocked out our capability to do the screen share, because our Apple IDs were already tied up in the Facetime call. However, without Facetime I can’t see his screen.

I’ll do a separate message for the issues I’m trying to fix.

No, it’s still there.

Here’s some Apple info on what to do if screen sharing is disabled: