I'm banging my head against a wall. I was given the invitation to the Google+ group, I followed the link to the play store. No matter what, I get this: https://play.google.com/store/apps/details?id=com.stackexchange.marvin&ah=xGxzuN2YjodMOBsHBf0lvKs231E
Even if I make sure that I have the right account selected. Even if I clear the Play store data, select the right account and download a new app.
If I try the Play Store link on my device, it always says "item not found".
So either I need a workaround for the above, or I should try signing up with an alternate Google+ account (not sure how).