somethings wrong with my keyboard, and I don’t know what

My S key ain’t responding all the time and I don’t know why I’ve cleaned it. I have looked at it. It looks like all the other ones but I don’t know why it’s not working it’s very annoying. I’m trying to get a hold of suport but my serial number isn’t coming up so I’m doing the next best thing. Hopefully someone can help me Or do I have to buy an entirely new keyboard, which would be stupid