Most (possibly all) buttons in the UI partially animate being pressed in response to a long-press without actually activating their function.
EG long-pressing the "play" button on the main screen causes it's pressed animation (it moves down whilst being held and turns dark blue) then when released it remains dark blue. No actual function occurs.
Since the long-press activates fairly quickly this could easily lead to some users thinking they are tapping but the application is not working.
Ideally a long-press on elements like buttons that have no special long-press functionality should be registered by the game exactly the same way as a regular tap.