Unable to share screen between two Macs after updating both to Sequoia

I've been able to share screens with several friends since upgrading to Sequoia, but not with my sister's MacBook Air.

If I instigate a screen share from Messages on my computer, Facetime will ring on her iPhone but there is zero response on her Air. If she instigates screen sharing from her computer (from Messages), nothing happens on her computer and I don't see anything on my MacBook Pro.

Steps taken so far:

1. Signed out of her iCloud account on both her iPhone and Air.
2. Restarted both the iPhone and Air then logged back in on both.
3. In General/Sharing/Content & Media, made sure Screen Sharing was on, clicked i to turn on Anyone can request permission to control screen, and Allow access for All users.
4. In General/Sharing/Advanced, turned on Remote Login, clicked on the i to Allow full disk access for remote users.

I would be very thankful for any suggestions on how I might resolve this!