thanks for trying Trio.
you can change to warrior, archer and wizard by T, Y and U respectively. also, please note that initially the abilities don't work as you haven't acquired it. you need to lose the game first, then use the points to unlock the abilities and retry from the same mission.
if things are still not working, it might be a problem with your device since i can play it fine.
let me know if things are working as intented.