The Problem
The scenario is a familiar one, I'm able to FaceTime and Message with someone, but we can't seem to share screens.
Here's the details that make it interesting:
Symptoms
- If I initiate the request, he gets an invite, accepts, but I get a no connection error message.
- If he initiates the request, I get an invite, accept, but nothing happens (he sees a no connection message).
- Connection fails either way.
But These Work
- I can Screen Share with other people just fine, so it's only with him.
- He and I can FaceTime each other, either initiating, and on multiple devices.
- He and I can Message each other, either initiating, and on multiple devices.
- He can access the full of the internet, with no issues.
His Settings
- His Firewall is off.
- His Screen Sharing is on. (Plus, we've toggled it.)
- The 'Anyone may request permission to control screen' is on.
- There so general VNC password, and that option is not selected.
- His Remote Management is off. (Plus, we've toggles it.)
- I have an Admin account on his computer, if that helps.
- We are on separate networks, separated by 200 miles, each behind a NAT router.
- He does not have anything between him and his router, like a firewall.
Stuff We've Tried
- We've checked for a NetAuthAgent process based on dated answers found here, but there isn't one.
- We've signed him out and back in to iCloud... no change in behavior.
- We've tried connecting to him with El Captain, Mojave, and Catalina... identical behavior.
- We've both more than tripled-checked the settings on his machine matches mine. He sends me screen shots to verify.
- I've verified I can Screen Share with other people, just not him. I used to be able to.
- He can't Screen Share with anyone. We strongly suspect it's his machine.
- We've tried using Messages to initiate the screen share.
- We've tried using Screen Share to initiate the screen share.
- We've tried initiating a screen share when running FaceTime (we know the bytes are flowing) and not running FaceTime (maybe it needs the i/o channel).
- He seems to have a rock solid internet connection with no drops, latency, or errors.
- We've rebooted, many, many times.
- I've looked on search engines, StackOverflow, and here for ideas. Nothing stands out.
Other Useful Notes
- He's Screen Shared with me several dozen times over the last decade. (He knows how.)
- It used to work all the time, before he took his computer to the Apple store and they reloaded a fresh copy of the OS on it. It wasn't working with Catalina, and they rolled him back to Sierra after discovering a performance bug in Catalina, plus he had an old 32-bit app he needed. The machine screams with performance, and hardware-wise it is the better equivalent of a current entry iMac.
- Everything else, is working fine... only connecting via Screen Share.
- We're both using Apple IDs to connect to one another.
Can anyone think of any other diagnostics things to try or other reasons it might not be working?
[ I'm strongly motivated to solve this, since he has Parkinson's disease and needs help when things get bad. ]
