I agree that it is usually bad connections, at least with my coach but then mine is 35 years old. If the starter is engaging but failing to turn the generator over it is probably low voltage to the gen starter. Put a volt meter on the starter cable lug on the gen, hit the start button and see what voltage you have. If the voltage is low, go to the battery and put the volt meter on the battery terminals, not the cables, hit the start button and see what voltage you have. If the voltage is low at the battery either the battery is discharged or dead, see if you can get it to accept a charge, if not see if your credit card will accept a charge
Jon
77 coach