Etsy isn't here in Forums. They won't answer you. Write to them directly if you want an answer to your question. Technical Issues is peer support from other sellers, and we can't answer it for Etsy.
You can simply go to Royal Mail and buy your postage online there instead and then input the tracking number on Etsy.
By the way, you have not set your shop location so this means that if anyone filters to the UK only (so many do!) then your shop has never been displayed in those results!!
You can fix it here and watch your views and sales increase:
