It sucks you still can't see the button though, I won't be able to fix it unless I change the build
You could consider adding a note to the game page on itch that people can try mobile if they encounter this issue. (by the way, I also do not understand the itch screen sizing thing... I had some issues with my game, but they seem to have disappeared somehow. I made my game in gameMaker and exported as GX.game instead of HTML. this solved the scaling issue for me.)