Cannot build for Windows Store Apps because of 'Invalid Characters in Path'

I've been spending the past few hours googling how to resolve it, going to all the suggested links and trying everything I can find (such as setting JAVA_HOME, etc.) but most of the solutions have to do with Android or the ones that I could try haven't worked.

Essentially every time I try to make a build, I get the error message: "Error building Player: ArgumentException: Illegal characters in path." and I have no idea how to fix it.

I was previously able to make builds for this project but now all of a sudden when I try to make builds for Windows Store Apps it doesn't work and I'm not sure what to try next to resolve it.