Hey! So I was able to load the plugin and mess around with it last night but now every time I open my project with it enabled it shows me this error message.

Hi CG249,
thanks for posting your message!
Can you please do the following for me?
If you want to reset my plugin because you cannot access the app anymore, please delete the uicustom folder from your game's directory. My plugin will rebuild it automatically.
I think http://www.yanfly.moe/wiki/Options_Core_VisuStella_MZ is a nice candidate