This bug is caused by all your hero skills slots being filled and the game wanting you to pick something to finish leveling up. If you want to continue playing, here's a fix:
https://drive.google.com/file/d/15fYMkNyIgYvuhInkZlGj6DX73tMXjHDV/view?usp=shari...
Thank you for playing! It's always fun to see people's play sessions! Go and beat that AI!
-TOIO
Edit: Fixed in current release
