ESP applicability

I am confused about my ESP coverage. I just recently bought a 2017 motorhome in October 2018. As luck would have it when I checked the dash AC when bringing it out this year it didn't work. Talking to my RV dealer, they say since I am the second owner, the original warranty is not available to me, which is why I got the ESP. However, this work was denied by the ESP as they say it needs to be covered by the original manufacture warranty. I am at a loss. Trying to figure out who I need to be talking to about this issue.