I have a friend that is having problems unblocking a contact. The contact was deleted and when she added the contact back to the contact list , everytime she logs in the contact appears blocked. When you check the privacy tab on the options that contact appears in the My Allow List. She's using messenger 4.7 She's using a computer in her work so she won't be able to update the messenger to the last version available. Can that kind of problem be caused by the old version of messenger she's using? If not what can be the problem?

This might be a server side problem with her account. Unless somebody else has something usefull to say about it I would try to contact Microsoft about it so they can have a look at the account.

Try cleaning up the lists with Noroom's Listcleaner

I would suggest having her log into another computer with her account. Like for instance yours. And unblock the contact sign out and back in and see if the contact is still blocked on signin. If not go back to work and try it. The other thing they can try is NoRooms list cleaner to delete the contact from their list off the server and readd them.

Thanks, I will give all your options to my friend!!

You can delete them from your "My Blocked List" once your contact delete you from his/hers.

One last thing... I noticed that my email address was shown in the ListCleaner program. I didn't deleted it because I didn't  knew what effect it will had on the messenger.