no sound and traoubleshooting tips

[irondiezl3]

very wierd never seen this before. everything powers on. stereo amp everything. yes i have no sound. complete silence even thought it seems like everything is working fine. i checked fuses in amp and stereo all wires and connections. idk what the culprit is the headunit or amp. i have a 4 channel amp running to speakers so the headunits internal amp is off. when i turn it off still silence. both the amp and stereo are a year old amp is mb quart stereo is kenwood excelon. any help appretiated also just noticed the protection light is on to that never happens wtf all my connections are clean and tight.