Hey there, Stephen Shelley
To unblock a user on Teams (Free), please can you click onto the ellipsis icon next to your name
Then click onto Settings
Then go to People which is found on the left-hand side menu
Then click onto manage blocked users
You will be able to see all users you have blocked on Teams. Please click onto unblock on the user you wish to unblock.
This should unblock the user, so they are able to communicate with you again.
Hope this helps,
Nathan