Yahoo decided to "improve" the groups by making them more like a Facebook site. Unfortunately, they didn't bother to test any of the changes to see if they even worked and switched some users over and not others.
I was one of the unlucky ones that got switched. For quite a while I couldn't see anything on the groups. Then I could see posts but not post or respond. It's still such a mess that none of us unlucky people can save records to the databases which means we can't order.
They just got the site up last evening and shortly after that I received my password so I can place orders!