I can't hear my guitar on my amp.(Crate amp)?

I have a Crate amp its on and connected to everythign incluuding the guitar, the guitar volume is on, the volume is turned up on the amp and guitar, theres no treble or b knobs, Ive twistd every nob by the way. it's on the main distortion (clean) I still cant firggin hear my guitar through the amp!!! what the frick is wrong??? When I pluck srtings, the lights light up on the tuner so obvisously the amp and guitar are connected,but I cant hear it