Are you sure that you have interacted with the generator while holding the correct item? That level has two items, a 'briefcase' and a 'charged briefcase'. One device dispenses the briefcase and the other charges it. The first repair requires a 'charged briefcase' but subsequent repairs may either require a charged or uncharged one (randomly). Perhaps you tried repairing with a charged one when an uncharged one was required? Took a while until I realized that.