Membership - MarketPress issues

Hi ,
I have the problem that when using membership and MarketPress, as admin I push the bottom "buy now", and I go to the store/shopping-cart/ page, no problem.. But any other member just cannot see that page, because is not listed in the list of pages available for using/looking in the editing of the level. Therefore the member just go to a non-access page, and cannot buy the product.

Any help??