If you have a float in the salt tank, make sure it is not stuck in the up position; that shuts off water flow into the tank.
Or you could have a blocked screen filter inside either end of the brine line if you have a screen. Or the screen by the injector or the injector or its throat could be blocked. Or the brine line flow control button could be blocked etc. etc..
What brand of softener do you have, or what brand of control valve do you have? If you don't know describe the face in detail as if I was blind and you wanted me to know what it looked like. Or, post a picture.