If user1 and user2 are getting access denied it might be worth double-checking that you have the user and domain right for them.
Try creating a new app with a text object with the expression =osuser() in it and then log in as user1 or user2 and open the app and see what it says.
PS. by " I get an access denied error when I log in" do you mean when you try to open the app? or before you get to opening the app, when you try to log in to the hub?