[Zubersoft]

I'm honestly at a loss as to what can be going on. You could make a video, but I imagine it would just show me that you're long pressing on the list and nothing is happening (especially if you can get it to work using a mouse). I listen for a very simple event called a holding event that is used for long press detection in various places in the application. You could see if the long press detection works to trigger the overlay when the Overlay Toggle Mode is set to "Long Press". You could try long pressing a file on the files tab when editing a song - you should see a popup message at the bottom right showing the full path of the file.

There must be a setting somewhere that is causing the long press not to work. If you go to cortana and search for "Pen and Touch", and then look at the Touch tab, do you have "Press and hold" set to "Right-click"? If you look at the settings for "Right-click", is it enabled? If I disable that, sure enough, long pressing no longer works to select things in MobileSheets.