Likely the gasket between the roof and AC needs tightening.
Remove the inner grill and there should be 4 bolts (one in each corner) that you can tighten up BUT DON'T OVER DO IT!
If it is new take it in for warranty?
Check the manual that you should have received with the camper for proper tightening.
Check this for answers.
2010 Cruiser CF30SK Patriot
2016 3500 Duramax
1950 Right Hand Seat GPS (she tells me where to go)