Kicker KMA600.6 Amp Ground Problem, Pontoon Boat

Hey all, I have a bit of a unique problem here and am at my witts end, hoping someone may have an idea of what the problem is. Here is what is going on:

I have a new pontoon with 2 batteries with a battery switch selector. I just installed a Kicker KMA600.6 amp with a kicker 4-gauge wiring kit. I have a JL Audio Mediamaster 50 head unit. I have ran the power and ground cables from the amp back to the house battery and all connections are good. Power cable measures 12.7 volts. Remote wire is connected to the amp power wire from the head unit and measures 12.12 volts. Problem is, once i apply power, the amp is immediately in protect mode. However, if I remove the ground wire from the battery and reconnect it while power is still applied, the amp power light comes on, the protect light goes off and the amp works flawlessly. As soon as I kill the power at my accessory switch that powers the radio or at the battery switch and then turn it back on, the amp is immediately in protect mode and will not work until I remove the ground and reconnect it.

I have purchased 3 of the amps listed above thinking there was a problem with the amp and all 3 do the exact same thing. I have also tried 3 different batteries. All 3 measure 12 volts or more.

Also, i have tried all this with and without the speakers and RCA cables hooked up, same issue either way.

Anybody got any ideas? Thanks in advance.

Pontoon is a 2023 Harris Cruiser 230.