When you scroll down the listing below the postage cost to... Preferences > Your settings click on the pencil icon on the right what does the postcode you have there state? Is it correct ? Use a laptop / PC try Chrome too when checking this, as the app and mobile browser can be sadly lacking for all options.
If it is correct and you are still blocked from completing your listing contact eBay Customer Services for them to explain what is needed here.
This is the easiest and quickest way to contact eBay Customer Services, for a Call Back option.
https://www.ebay.co.uk/help/eua?id=5275&mkevt=1&mkpid
Lines open for ' live agents' 8 a.m. - 10 p.m. on weekdays
9 a.m. - 6 p.m. on weekends.
Automated agents will be available on chat outside of the above hours.
I recommend contacting CS first thing in the morning as there's more chance of Dublin answering.
@domenico401
