Troubleshooting screen sharing over Messages.app

[Speed38]

If I am posting this in the wrong forum, would someone kindly point me toward the correct one?
I have a 2015 iMac, FusionHD, macOS 12.1.2.
I am trying to help seniors dealing with problems with their Macs.
90% of the time I am able to use Messages.app to view and control their Macs.
10% of the time I will extend the invitation to share screens, they will never receive it, and the attempt times out with something like: John Doe is not available for screen sharing.
I will carefully walk these folks through the process of making the proper changes to Sys Prefs > Sharing by following Apple's instructions to the letter, but the same thing happens: they never get the invite.
However, when we turn it around and they send me an invite to view their screen, it works, but of course it's not possible to control their screens and I have to go through the laborious, time-consuming process of "Click there, no, not there, to your left, etc.".
I have searched everywhere for an answer to this question but came up empty handed.
I wonder, could it be a firewall setting on their modems/routers that is preventing them from receving the invitation to screen share?
Please, can anyone help?

 

[satcomer]

Yea you computer can't support now M1 Macs! grade your system to m1 16g Mac mini and you won't have the problems!

 

[Speed38]

You may be right, but I don't think so. I think she does not have Messages set up properly.

 

[Speed38]

I have checked, via a Zoom session, the Messages settings of a fellow who never receives the invitations I send him and I can see nothing wrong with them. They are essentially the mirror opposite of my own settings, screen sharing is turned on, notifications in messages are turned on, he has only one AppleID, etc. Despite all this, my invitations to him are never received. Why is that about 10% of those with I try to screen share using Messages fail to receive the invite. So damn frustrating!

 

[satcomer]

I have checked, via a Zoom session, the Messages settings of a fellow who never receives the invitations I send him and I can see nothing wrong with them. They are essentially the mirror opposite of my own settings, screen sharing is turned on, notifications in messages are turned on, he has only one AppleID, etc. Despite all this, my invitations to him are never received. Why is that about 10% of those with I try to screen share using Messages fail to receive the invite. So damn frustrating!

He could check if he only receives message from his contact lists or something along that line!

 

[Speed38]

Thanks for hanging in there on this thread.
I just checked the Preferences in Messages and don't see that setting.
Can you steer me in the right direction re where to find those settings?
Thanks

 

[Speed38]

On second thought, ignore my last email: I am already in his Contacts List.

 

[Speed38]

I had a similar experience with a senior in FL whom I help. I sent the invitation, she received it and accepted it, I saw her screen for about 2 seconds, then screen sharing quit with no indications as to why.

 

[satcomer]

Thanks for hanging in there on this thread.
I just checked the Preferences in Messages and don't see that setting.
Can you steer me in the right direction re where to find those settings?
Thanks

Also in the Messages.app Presence file under messages tab is to receive messages from whom? Also he should look too!

 

[Speed38]

Actually, under the [Messages] tab are the telephone numbers and email addresses at which the recipient can be reached.

 

[Speed38]

I give up. I have tried everything and yet, with about 10% of those with whom I screen share over messages, they never get my invitation and the screensharing app just times out.

How very frustrating that I have that subset of about 10% with whom I just cannot screen share.