It's quite frustrating with the issues on the GHA App. It's quite similar to what some of you have raised in November last year.
I made a booking via GHA Discovery way back in August 2024 for a stay at NH Collection München Bavaria in April 2025. Recently I checked the prices again and there is a flash sale on-going and prices have dropped for the room I booked. However, I was unable to modify the booking and the only way was to contact the hotel. I believe some of you have encountered this as well.

I sent an email to GHA Customer Care and their response was that this was out of their hands and for me to contact the hotel instead for any changes. No help there.

I did just that and is still waiting for their response. In the meantime I made another booking at the cheaper rate, and now this booking doesn't show up in GHA Discovery (both app and website).

Thankfully, both bookings can be found in NH hotels via a search, so hopefully NH can help me cancel the booking manually.

It's just frustrating that in this time and day, such things have to be done manually instead of being seamlessly done via the app or website.