[Cupid]

I presume you are following the sequence detailed here ?

Is ebay.com the usual site that you use or one of the other satellite sites ?

If it isn't, have you tried logging into that site directly, just to check if Ebay are requesting something from you, on that site, when you do so ?

[Diamondbite]

I am unable to authenticate as a new user. I get to the part where I am asked to login to Ebay. After logging in, instead of being redirected back to Gixen, I am directed first to a page with the message "Thank you. If we ever need you to let us know it's really you, we'll use the information you confirmed to do it."
with a button labeled "Continue." Pressing this button leads to an ebay error page that says "We looked everywhere. Looks like this page is missing. If you still need help, visit our help pages."

Thanks !