This a intermediate problem on Onan 7.5 dkdf. When press start button nothing happens at all but you can gently press down on left side control board all works. It then may work for days. It is Onan board 300-2604 , think it probably a bad board.
If the board is properly secured, I agree.
Tim
If you have a spray can of electronic cleaner, it wouldn't hurt and might help to give the entire board and especially the connectors a good squirt.
I had remembered someone with this same problem a while ago. I used the new and improved search for " press down on control board" it came up with this. And is has the same subject line.
Generator won't start (https://www.foreforums.com/index.php?topic=48399.msg488606#msg488606)