Inverter / Converter won't switch over when on Gen

So I've been having issues with my xantrex inverter / converter on working with my generator. No pass thru nothing, no charging. Nothing. Works fine on house and pole power. Just won't on the Gen set. I've tried 2 different Gen sets. With the same result. I have to use a seperate battery charger to charge the trailer batteries. Very annoying. Can't use inside 110 off the Gen Set either as it won't auto switch to shore line.
Looking for some ideas.