In the new iOS apps released this week, your existing program change values won't appear on the MIDI preset edit page if you added MIDI devices before the app supported MIDI port routing. You can fix this problem with a simple update to your MIDI devices:
1) Navigate to Settings > MIDI Devices.
2) Select a MIDI device.
3) For the Port setting, tap the X next to All to clear the value. Next time you view it, it will say All again, but it will be updated.
4) Repeat steps 2 and 3 for each additional device.
I will submit an automated fix with app version 4.2.2. Unfortunately, I can't do that until Apple approves the version 4.2.1 that I've already submitted.