1st time boondocking and could not get our AC to work

https://www.ebay.com/usr/applianceandair?_trksid=p2047675.l2559

I had the same problem your having and have a 3500 champion inverter gen. I finally bought one of the above and now its starts fine. get the starter and the capacitor. all that soft start kit does Is what your doing by starting the fan then a few seconds it starts the compressor.
im think the onboard charger is a problem if its on they can be disabled at the breaker panel?
Jay D.