Best answer by woz
As it's a direct debit the only reasons for it not being paid are either that you've cancelled it or there are insufficient funds in your account and the bank won't pay it.
Either way you should contact the team to explain, you'll find in the second case they may want to help you (sympathetically) to either amend your payment plan, or agree a payment with you, or take a one-off payment.
In answer to the question I don't know for sure the process, but I'd expect PP might try to claim it again if the bank refused it (I'm not sure perhaps
As far as placing a mark on your credit file goes I don't know under what circumstances that would happen, I suspect if it was one payment and you took steps to pay it you'd probably be OK but best to ask them directly, go to help, ask wattbot, type message the team and ask.
What happens if you miss a payment on the day it is due