Not sure if this will help, but try clearing cache and cookies, perhaps switch devices and browser.
If using the app or mobile browser switch if you can to a PC / laptop, and use Chrome, that works best with eBay.
Try and see if the above helps.
If it doesn't, contact eBay Customer Services who have access to your account, and can perhaps see why you are denied access here.
The easiest and quickest way to contact Customer Services is through this link, for a Call Back .
https://www.ebay.co.uk/help/eua?id=5275&mkevt=1&mkpid
On weekdays lines open between 8 a.m. and 10 p.m. - 6 p.m.
Weekends lines open between 9 a.m. to 6p.m.
@twoflyingfox
