I'm going to guess that you allowed your iPhone update past the last working iOS version. All my iPads are hacked so they only update if I allow it. They won't even download the update until I remove the hack. That said...
I believe legacy versions of the Go App stop working around iOS 13 or 14. I allowed one of my iPads to update to iOS 17 and my legacy versions of the Go App, Go 4 App and GSP immediately stopped working. I don't use that iPad for drones any more, so I just deleted the apps. I didn't try to update the apps, as I won't use modern versions anyway.
D