You will be able to enter the Megalockers premises with the access code, but you will not be able to access your locker until you have paid the penalty, which can be 0.95€ for a range of 1 to 15 minutes, or 1.9€ for a range of 15 to 30 minutes and so on.
Once on the premises, you can consult on the module screen the payment link with the total settlement according to the delay time.