SR 6006 no sound from speakers but head phones have sound

I don't have your model, but I have two Marantz NR1504 receivers. They power up, and then the output is connected to the speakers by a relay (you can hear it click) but only after the receiver is satisfied that there are no shorts on the output that would damage it. This is called protective mode. Maybe your receiver is staying in protective mode, or a fuse on the outputs is blown. try disconnecting all speakers, and reconnect one by one?

Had the same issue. I unplugged the system for a few minutes and it fixed the issue.