You might want to let Support, support@singularsound.com know which version of your phone’s operating system you were using.
I was using iOS 16.5 and although our symptoms were sort of similar, I was able to resolve mine. Hopefully you’ll resolve yours too.
While you wait, here’s something else you can try: delete the MM app from your phone and then download and reinstall.
Place your phone next to your pedal and go back thru the process to install the firmware and Default Modes. Follow the instructions Brennan posted here MIDI Maestro Firmware 1.1.9 and MM apps 1.6.x and NYHC reiterated at the next to last post in that thread. Good luck—I’m sure you’ll get it installed and working.