Does the amp trigger if it is the lone item connected to your avr? In other words when it sees the full voltage it is designed to see and not whatever is produced when split between more than one piece of equipment. If so I wouldnt blame the amp but be more inclined to be unhappy with the shortcomings of the avr having only one trigger output.

LFR 1100s QS8s QS2s ADA15000-4, VP 150, M 3s,Polk CSI A6, Klipsh B10B, SVSPB2000,PSW125x2