If you have not signed in to your account recently, it may have been removed by eBay.
Several years ago eBay required many users to update passwords; accounts that did not comply were removed to prevent them from being hijacked and used for scams.
Try signing in with your original username and password if you can remember those; or try using your original email address and password instead. If you remember your username but not your password, you can request a temporary password, assuming you still have access to your original email or text number.
If you are able to register a new account using the same email address you used to register the original account, that would be an indication that the old account is gone.
