The app is problematic. It could be a glitch, but it might also be working as intended as the app does not have the capabilities of a computer.
WIsh I could be of more help. I don't use the app. But you can check out the Mobile Board or the App Board and they might be more helpful for you. Or someone else may come along here soon as well.
Instead of choosing the Selling Board, just run your eyes down the list to the other Boards and you can click and choose them that way.
