Hello, I'm new on krita. when I first downloaded it, it worked perfectly. After some time, the canvas stopped reacting. Everything else works. I can add layers, but I can't do anything on the canvas. I've seen some people write about this issue and they just had to disable OpenGL. But when I tried to do that, there was no OpenGL option. Does anyone know how to fix this problem?

First check whether you haven't got a little selection in your image which you're trying to paint outside of.