Some general suggestions if you are having problems with verification or pages are not loading properly:
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.
In some cases, pages load better with an ad blocker or script blocker, though.
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 and update your settings 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.
If you are following a link, try opening the link in a new tab or in a new page if opening in the same browser tab is not working for you.
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.
Check your browser for updates here:
https://www.whatismybrowser.com/
If there is an alternative link or path to the page you are trying to use, such as going to ebay.ca or ebay.co.uk and updating your info there, or using the eBay app, see if an alternative method works better for you.
