Make sure the audio system for sound is on including the FOH console (Sound board)
Turn on the iPad at the keys rig by using the code 0812 and make sure the USB-C is plugged in to that iPad. Everything runs thru this cable including signal to the sound board.
Once iPad turns on, open the Sunday keys app. Once it fully opens, click on the keyboard and you should see a signal going thru the top of the app
If for some reason you don’t get a connection, check the USB-C cable going into the hub and then from the hub make sure all cables are fully connected