The Cruxia mini game?
I tested out the the buttons you mentioned and they work just fine. In order for the options selected to function, you have to press the enter key or click on the option you’re wanting to choose.
In this mini game, you can only fight Cruxia or look at her stats by pressing “Act”. The “Spare” option does nothing as it is scripted to fight Cruxia.
To summarize, it’s not a glitch. You just have to hit a different key aside from the “wasd” buttons or the arrow keys or click on the option you’re wanting to choose.