I run a 10-51T casette on one of my eMTBS and it's perfect for the steepest sections.
43 is certainly not enough for mountains or even hilly tracks in downs and so on.
Yes, I have a similar problem, along with many hundreds at the Google Play Store rating Giant one star, the app demands to be updated in order to connect, and then goes into a loop of failing to update and demanding to update.
It is a very bad look for Giant, considering the prices and expectant...