Have you ever used the Onkyo to trigger two items at the same time before? Maybe its trigger voltage is less than the 2200 requires. Since you can trigger the 2200 from other sources, the Onkyo would be suspect. The 2200 manual says 6-35 volts for trigger. Measure the trigger output voltage and if it is lower than 6 volts you may need a repeater. Does the "music" setting function as the trigger? Just for curiousity sake, how long after the system is off do the 2200 stay active?
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Music system
Model 990/7500/Magnepan 1.6 QRs/Technics SL1200 MK2/Aperion S-12 Subwoofer/OWA3/Sony NS75H DVD
APC H15 Power Conditioner

TV System
Large Advent Loudspeakers/ Polk center/Monoprice surrounds/Panasonic Viera 42 inch/Onkyo HT-RC260/Sony BDP S590/Directv


Home Theater System
Onkyo PR-SC886/Outlaw 7125 Klipsch RF-82 L/R,RC-62 center, RB-35 SR/SL, BENQ HT1075, Outlaw LFM1-EX/OPPO BDP-83/Directv
Harmony ONE
Blue Jeans and Monoprice interconnects
APC H15 Power Conditioner