Fixing small Unity3d problem to open pdf -- 3

The task is solving this question https://stackoverflow.com/questions/71327455/playing-scene-selecting-background-instead-of-button

This was already working before but it's not loading the pdfs anymore.

I can give you access to my machine by AnyDesk, I will need you to show me how to fix it

This should be super simple for someone with experience

If you want to be considered, don't put a copy paste proposal