Rockin Rollin will display "HELP" on the score display when the game owes tickets. To clean the error code replace tickets if tickets are out and press and hold the service button (On backside of ticket door)for 5 seconds to clean the ticket error. If the game is not out of tickets and the "HELP" error is shown the issue could be with the ticket inverter PCB below the ticket mech, or the input chip for the ticket return notch could be bad causing the game to believe it is out of tickets.
Remember the game will continue to "bank" tickets until the error has been cleared by pressing and holding the service button for 5 seconds.