Do both computers need to be the same OS? When I connect a MacBook Pro to my ATEM 2 M/E Broadcast 4K it asks me to install a software update. I did that and then when I connect a Windows 10 laptop it asks me to install another software update. When I switch back to the Mac it asks me to install yet another update and the process loops.
Tim, the reason ur seeing this is most likely due to you having different release vers of the control software between the differing computers. eg one might be running 7.5 and the other 7.4 If one is running an earlier or later version than the other the switcher will see it as a needed update and ask that it loads that version.
Simple fix, make sure both computers are running the same release version of the Atem control software.
Just to confirm, that having installed the latest (same) version on both a Mac and two Windows laptops, I am able to connect to the same ATEM with all three at the same time. This allows us to operate multiple M/Es and MediaPlayers without switching tabs.
One thing I would say though - use an Ethernet connection to each machine, and don't rely on WiFi.