Try using another browser. Preferably the latest version with default settings and no add-ons.
I get that verification error trying to sign in to ebay.co.uk directly with username and password using Firefox, but I was able to sign in using Chrome or Edge. Not sure if the issue is specifically with Firefox or just due to past cookies or cache.
If you have a social media account linked to your existing eBay account, try signing in that way to see if that is any different.
If you are able to sign in to the community, you may be able to your eBay account through the My eBay link by clicking on your eBay picture icon in the upper right.
Or try reaching your eBay account through the eBay app.
