Hi Tony! Thanks so much for checking out the demo. The battle button controls can be assigned on the main menu if you go to Options, then Controls, then look at the rows labeled Battle Buttons 1 through 4.
It is possible that if you have a gamepad plugged in, then control is being directed away from your keyboard to the gamepad. The assigned buttons shown in the Controls menu should confirm whether MonCon is expecting you to play it with a gamepad or with the keyboard.
Hope this helps! I'm happy to do more in-depth troubleshooting with you if you like.