I got the link from eBay (it's not under any city--I tried to look for it for a long time and couldn't get it either because I also was trying to use my account) and I think it's a special deal just for eBay so that you can't use your Groupon account but you have to type in your info again (use the same as your Groupon). I wasn't sure if it's because they require you to have a PayPal *and* eBay account in order to get it but it says on the right when you checkout that you have to type it in unfortunately.
Re: PSA: Groupon: $7 for $15 on eBay