You are registered in the UK, but you are currently signed in to the US ebay.com site.
You may have better luck with verification on the UK site, particularly if you are trying to do anything involving your sales:
https://www.ebay.co.uk/
If not, or if you are trying to use the US site, here are some general suggestions for dealing with verification issues:
Disabling ad blockers, pop-up blockers, script blockers or other privacy tools on the sign-in or verification page can help; many of those have settings that can interfere with verification. You may be able to turn them back on once you have signed in and updated your eBay cookies.
If you are using Firefox, try disabling Enhanced Tracking Protection on eBay using the shield icon to the left of the page address.
If you are able to sign in using a private or incognito browser window, that might indicate a problem with a corrupt or blocked cookie. Try erasing just your eBay cookies manually in that case.
If you are routinely clearing all your cookies, you will likely have to go through verification again each time you sign in.
Or try a different browser -- preferably the latest version of a popular browser that you do not normally use and one that has no add-ons or extensions installed.
More things to try can be found here (note that links are for the US ebay.com site):
https://community.ebay.com/t5/Member-To-Member-Support/Whatsup-with-3-levels-of-authentication-just-...
