Using custom progress view or timers in live activities or dynamic island was never possible. It probably worked for you when you tested in simulator or linked to a debugger in Xcode (in this case the app is running in background vs in real life scenario it's suspended after ~10 seconds).

My watch app is launched but handleRemoteNowPlayingActivity() in WKExtensionDelegate is not being called, so I cannot configure the app. Has anyone solved it?