nau 260 with mt6502bs

[sl45082]

on the boat its a mb quart cd radio that has rca out for "rear speaker" one red/white rca connecter. using a 2 channel nau 260 amp. mounted the tubbies on the tower and ran the speaker wire through tower tubes. Brand new amp and tubbies. Head unit is existing and runs two speakers fine already.
I have good power and ground to the amp, as well as the switched 12v (blue) control so it powers up and down with ignition. Lighting the small green led on the amp. also on the amp is a red lamp (not the one near the green led) on the other side of amp by the company logo and model name. This is lit whenever i put the 12v power to the unit. I have all the speaker wires connected to proper plus/minus-red/black.
I get no sound. I have set the frequency to FLAT and tried adjusting gain - but nothing. No hiss, whine , pops or boot up sound from amp.
I have no idea if there is sound coming out of the MB quart cd radio head unit to those rca connectors that i have patched into my amp. So to test I was going to use another audio source with an rca cable to feed the amp.
Any other ideas why I would get no sound... thanks for any help.