Grade booster won't work

Hi in the most recent online mission when I defeat a boss and get a grade booster it won’t let me use it. It has the choose button but nothing happens when I hit the button and there no way to exit the screen messing up my game. I know the game only cost me .99$ but there seems to be a whole lots of issues with this game. It’s a fun enjoyable game but all these bugs are starting to turn me off the game. If anyone knows a way around this bug please let me know since I can’t continue the om till this is fixed

Do you even know how gradeboosters work?

They boost your grade of the monster you choose …

Yeaaa when u updated your arks grade , did u see it change ?? Or it worked but didnt realize it ?