This was a super weird issue. Across Center was working wonderfully for me across two late model Macbook Pros each running High Sierra 10.13.3 I took one of the laptops away on a trip and when I came back I expected to be able to plug everything back in and have it work. Well... it did, for a little while, but then I restarted one of the laptops. The issue I was having was that the bluetooth connection was constantly connecting and disconnecting over and over and over making the client computer uncontrollable. Thing that I tried: - Turning on/off Bluetooth, unpairing, reconnecting, etc. - Restarted both computers - Deleting the apple Bluetooth files and let them get recreated on restart - Use the Bluetooth debug menu to unpair all devices and reset the Bluetooth module on both computers - Unplug all USB and other devices, reset both computers - Reset PRAM on both computers - Uninstall and reinstall Across Center on both computers - Probably more at this point that I can't remember Weirdly, I accidentally stumbled across what fixed it: - I ended up clicking on "Across Uninstaller.app" and selected the checkbox to remove all settings. Then, I clicked "Ok" and when it asked for my password I hit "Cancel". The uninstaller reported that the uninstall failed but after doing this on both computers, Across Center stayed connected and seems to be working as seamlessly as it was before I had these issues. I'm mostly adding this to help anyone else but also incase one of the developers can figure out why this happened and how to fix it. Any comments?