When I play the sample, it sounds like normal, but the virtual keyboard, which should have been playing until yesterday, is no longer playing with instruments and presets. If it is a sample, it will be played.
Whichever audio backend you set, it's the same, and it doesn't change when you set the Buffer size to max, what should I do?
Have you tried selecting the instrument or preset after opening the virtual keyboard? Because I think when you have nothing selected it won't play anything...