My Line 6 Spider II 210 won't make any sound from the guitar. When the amp powers on, the speakers pop a little so I know they are connected right. All of the lights are on and the channels can switch easily and act normally. When I plug in the guitar, it won't make sound at all from the speakers. But if i turn the master volume and channel volume all the way up, you can hear it but it's very distant and quiet sounding. What can I do to fix this? I've checked for loose places but there aren't any in the fuzes or anywhere else. Help?