This has come up one time before, but thankfully one of the moderators on the server knew the workaround:
1. Open the game
2. Press Shift+G (This will open a Renpy debug menu)
3. Select ANGLE2 Renderer. Close and re-open the game and it should work.
If it doesn't work, then it's a GPU rendering issue and you'll need to update your graphics drivers. This is why it'd also be carrying across to other VNs assuming they're all made with Renpy.
Just in case your menu is screwy, here's one to guide you. You're looking for the third option in the top left set of options.
