If you have more tha one contact invitations to accept you noticed that if you click the invitation yellow box it opens a web browser windows but the link does not work anymore .
you must do the following in order to add all the contacts
--------log off from windows live messenger 2012 -----
dowload butterfly messenger https://messengergeek.wordpress.com/2015/03/25/butterfly-messenger/
extract it (right-click on the mouse and choose ‘extract’’)
3)log in with your e-mail and password
4)accept all your invitations (it will ‘pop-up’’ window )
5)log out from butterfly messenger by clicking ‘‘signout from everywhere’’
6)log in on windows live messenger 2012 all your contacts have been added and you can chat.