My grandfather has an iMac running OSX 10.8. It took quite a while over the phone, but he managed to get TeamViewer 12 installed, which is the latest version that works on 10.8. I have access to a linux machine and a MacBook with OSX 10.14. I tried TeamViewer 12 on both, but whenever I tried to connect using the "Your ID" shown on his screen, I was presented an error that the remote Team Viewer was too old. But we were both using TeamViewer 12! I had him confirm via "About Teamviewer".
Remote troubleshooting over the phone is quite painful and due to COVID nobody can stop by to help him out. Anyone have a suggestion on what might be wrong?