I was playing around, mapping my development FileMaker Server to port 10443 instead of 443 After the login screen, I set the development server address to filemaker.deanayalon.com:10443 , which is mapped to my development server and working. The Devin client was trying to connect, and neither succeeded nor failed, it was simply stuck on “Connecting to Engine…” Trying to restart the app did not work, as it was still trying to connect and not falling back to allow a different input I then tried to reinstall Devin, but it seems my development server address is saved on my account, so that also didn’t help (or, perhaps some data persisted) Only stopping the FileMaker Server itself and restarting Devin allowed me to get back to input a different server URL I then tried https://filemaker.deanayalon.com:10443 , as I thought the problem may be an unrecognized protocol, but this did not even try running Aside from maybe implementing connection to custom HTTPS ports, there should be a 'cancel' button during the connection process