Musescore won't run

I'm on a Linux Mint 20.1 system. The Musescore Flatpak has stopped working recently. I can install/uninstall it, but it refuses to run. Here are the results when running from my terminal:

~$ /usr/bin/flatpak run --branch=stable --arch=x86_64 --command=mscore --file-forwarding org.musescore.MuseScore @@ %F @@
Warning: QT_DEVICE_PIXEL_RATIO is deprecated. Instead use:
QT_AUTO_SCREEN_SCALE_FACTOR to enable platform plugin controlled per-screen factors.
QT_SCREEN_SCALE_FACTORS to set per-screen DPI.
QT_SCALE_FACTOR to set the application global scale factor.
Gtk-Message: 10:35:11.109: Failed to load module "xapp-gtk3-module"
Gtk-Message: 10:35:11.149: Failed to load module "unity-gtk-module"
Gtk-Message: 10:35:11.149: Failed to load module "unity-gtk-module"

(mscore:2): GLib-GIO-ERROR **: 10:35:11.149: Settings schema 'org.cinnamon.desktop.interface' is not installed