I would suspect bad gas on a new unit. Ethanol fuel sits, then water separates to the bottom, maybe some water in tank. More fuel might not matter as water may still be there on the bottom of the tank. I would drain and put fresh fuel in, and eliminate that first, or maybe the spark plugs are fouled. Lots of times the machines are started and not allowed to warm up while being moved back and forth at the dealer, and plugs get fouled, I'm sure others will chime in with other stuff to check.