PPSSPP Games load with sound but no video?

[LunaMoo]

It's not common problem. First of all, recallbox doesn't use proper PPSSPP emulator, it's uses it's libretro port which is awful and quite limited by it's "retro" design choices, it's much slower than proper PPSSPP so it's possible they're using speedhacks like disabling buffer effects by default and this in some games will simply disable all the graphics which is normal as you can't disable primary way of game doing it's graphic and still have it display something. Libretro port is also less compatible and more buggy compared to actual PPSSPP, so it's possible it just doesn't work for whatever reason.
Those are PPSSPP forums, not libretro, so can't help you much with it other than recommending to use proper PPSSPP emulator with default settings.