Adding to John's correct answer, some buyers as indeed sellers too, do not realise that the bringing of that code for a seller to scan is essential, as it's the only proof a seller has now that cash on collection has been dismissed from the party, that the item has been collected.
Send the buyer a message for them to chek their emails and eBay messages , pthe 6 digit QR code has to be there. They can then send you those numbers for you to manually enter on the left hand side of ..... Confirm Collection.
If they don't, no worries, it just results in a longer wait, up to 21 days for that payout.
@georgewaldrons12