Worst case here you could say to the buyer you are going to send an
empty envelope or box with the label they purchased at checkout, some
people are generally understanding so it may be worth a shot and will
avoid running foul of eBay’s automation.
From what I can see, I sense they've cut out the middleman that handled
the postage side for them and Simple Delivery is eBay's in-house
solution to replace it. This would explain why they can't translate the
framework from the 'Get Postage Label' to...