I made sure that both the L/R RCA cables were working by using only one at a time and they both produced sound. I could take apart the center console and double check that I hooked up to the correct L/R ports in the head unit.
I'm pretty sure this amp is the same as some other amps: Polk Audio's 5 channel amp and JAD 900.5 amp. The JAD manual is better but not by much
https://www.nvx.com/content/NVX_JAD9...ual_052316.pdf
https://www.carid.com/images/polk-au...005-manual.pdf