I suspect that corotor, I've had a bunch of those things tear up. C-band will work fine, but ku will be stuck on one polarity or not work at all. This happens when the little plastic rod that turns the ku-probe breaks in two. I'd pop that cover off the end of the feed horn, have somebody change channels on the receiver and watch the parts to see if the probes both move when you change polarity. That, or bad ku cable, connectors , or ku lnb has died. Hope that helps.