Account appears unused for selling for a long period and there have been some changes --- worthwhile to completely check and update your account details including placing current UK  Banking account details on file for Managed Payments >

https://www.ebay.co.uk/help/account/changing-account-settings/changing-account-settings?id=4193

https://www.ebay.co.uk/help/selling/getting-paid/registering-seller?id=4792