No plugins in mixer and no playback

Hi! I have a Musescore project of the intro section to the song "golden hour" which uses just a piano instrument. Used Addictive Keys plugin instead of the basic piano sound which I tuned inside of the plugin to A=432Hz cuz the song uses that tuning. This worked fine the first couple of times I opened up the project, but when I open the project now, I can't start playback and there is no plugin on the instrument. It is also not opening the list of plugins/basic sound if I try clicking. I can access the notation and copy/paste just fine, but it seems like playback and mixer window is bugged/corrupt. Any fixes?