I removed my inverter for unrelated repair access; now it's bad?

When I replaced my ABS actuator assembly , I removed the inverter (all connections except the hose) and put it back when I was finished. But when I started the vehicle for the first time, I got all the dash lights (tire, VSC, ABS, triangle). No power steering, drive, or reverse.

Eventually I learned the 12v auxiliary battery was low; I figured that since I didn't unplug the 12v system while doing the repair (dumb, I know), the fob handshake may have been engaging electrical systems while I had it apart.

After a full-night's charge and several test laps around the block, things seemed normal. I should have tested the voltage again, because shortly after all the same lights came on, I lost steering/transmission control, and the engine threw a P0A08 code. Luckily I was able to limp it home with a Walmart battery connected in parallel.

And whadduya know, P0A08 is an error code for the circuit responsible for recharging the 12v auxiliary battery. My question is this: is it more likely that my inverter broke during the repair process or that I have a bad wiring connection somewhere? All the wiring harnesses in/around the inverter seem to be securely-clipped. Maybe some brake fluid is shorting out a connection?

Looking for any diagnostic suggestions before I replace the whole inverter.

 

Thank you! that's exactly the kind of resource I'm looking for.

I'll also reconnect all the things and see if that helps.

 

Whelp, I found the plug I forgot to reattach! What a satisfying click Car's back in action, no lights, and I'm feeling confident on the road again!

I'm thankful for your suggestions and for this forum that's saved me more times than I can count!

-205k miles