eBay do not have to consult their members when they wish to change their house rules, but this was announced earlier this year that it was coming in from April 15th, and it's been a very slow roll out.
You do not have to have a printer. Photograph the code with a camera / iPad similar device take that to your PO they'll print off the label for you from that code.
If you are asking about combining postage for multiple purchases this is still a technical issue and cannot be done.
If postage was purchased though Simple Delivery and you now post all the items together the buyer will receive a refund for the unused labels they paid for, might be worth sending them a message explaining this, and that it may take up to / over 30 days for the refund to appear.
If you paid for the postage, that is, seller pays, then you need to manually cancel the label for a full refund and do so within 14 days.
The best way forward would be to cancel all items, of course, with the buyer's acceptance, and relisting them as one, so there's one important tracking number, one postage price. Ensure any message to your buyer makes it very clear the reason why the items are being cancelled, that they are to be relisted on eBay again, for the buyer to buy, leave no room for doubt that this is Not an off eBay sale.
Some sellers are leaving a message on their listing, for example..... ' If you wish to buy multiple items, please let me know before buying, I will relist them as one listing so only one postage cost is charged, combining postage is not currently possible. '
All a faff I know, hopefully in time, it will all sort itself out ! 🤔
