Power Issues - Generator not starting - brand new batteries

Schneider wrote:
I have 13.65V at the leads going in to the generator when the truck is idling, and 12.8 or so when the truck is off suggesting that all is well with power getting to the generator. Good voltages across the inverter and converter as well.

You need to check the voltage at the generator when it is trying to start, otherwise there is no current being drawn by the generator and so there will be no voltage drop if there is a high resistance connection. Also check the battery voltage under the same conditions.