It seems that the link in their email is broken. This one from live chat
worked for both of my seller accounts:
https://signin.ebay.com.au/ws/eBayISAPI.dll?SignIn&UsingSSL=1&pUserId=&co_partnerId=2&siteid=15&ru=http%3A%2F%2Fcgi1.ebay.com.au%2Fws%2FeB...
