Try the following:
Turn off the HDMI "communication" feature of the TV. The issue with HDMI is that all connected HDMI devices need to be "vetted" before any signal transfer takes place. Maybe you can fool the Receiver into not seeing the TV, or maybe your TV should be on standby with an active "communication" with the Onkyo receiver. Try both ways and see if anything works..
Turn off the HDMI "communication" feature of the TV. The issue with HDMI is that all connected HDMI devices need to be "vetted" before any signal transfer takes place. Maybe you can fool the Receiver into not seeing the TV, or maybe your TV should be on standby with an active "communication" with the Onkyo receiver. Try both ways and see if anything works..