I’ve had my washer a few years and never had an issue. Today my daughter went to start a load and it wouldn’t turn to the cycle she wanted. I was able to but took effort to do it. It ran just fine but I’m not sure just what part I’d need to replace or anything. I’m not sure what would cause it to work yet not let the knob turn
A model number may help others help you.
Remove the knob from the timer just to be sure that it is not the problem.
If it seems OK then I would replace the timer.