Receiver puts up PROTECT message
Not enough information provided - problem is likely impedance / load related. Receivers / amplifiers usually self-protect when the resistance they expect to see as provided by a loudspeaker is too low, or bypassed by a shorted circuit. Check your loudspeakers' impedances - impedance is measured in ohms. The loudspeakers' native impedances, as-built, may be too low for the amp. You can check the amp's requirements in the spec's section in the manual. If the numbers check-out, then put a multimeter on each loudspeaker to check their impedance. A failed loudspeaker can have a tanked impedance, thereby cascading instability to the amp. If you are driving a dynamic arrangement of loudspeakers with room-borne volume controls, a multi-meter won't likely reveal accurate impedance, you will need an Impedometer to test. And, most importantly, make absolutely certain that there is not a single strand of conductor errantly shorting at all terminations.