Any repair geniuses? MRD-F752 protection issue

[idrivea911]

I've had an MRD-F752 5 channel for a few years. Most recently I had it installed in my Subaru, and was just using it to run my subwoofer. I took it out for a few months, then ran some additional speaker wire so I could use all 5 channels again. But when I hooked up power grounds and signal, it came on with Power light flashing red, music light amber, and protection light solid red. According to the manual, this means (in order) abnormal circuit, muted music, poor voltage under 10V. Via DMM, I have a good 13V across the terminals, and the ground is tied to my rear strut mount and has good continuity to - batt terminal.

Then, just to make sure, I took out the amp, and powered it using a 14v 15A power inverter that I have on hand, to rule out car wiring issues. And I have good 13.5V and still the same light patterns.

I pulled the bottom plate off the amp, but don't really know what I'm looking at. The main 80A fuse is good. The fans are on, so power is getting at least that far. All the ribbon cables are tight. I don't see any bulges on the 6 main capacitors. I think the 3 pin things are diodes, and none look notably melted or anything. Anyone aware of any common issues I might be able to trace?

Dunno if a pic will help...