Hey
@Player_fmqtsimf,
If you've accidentally blocked someone and would like to unblock, you can use either of the following methods:
Unblocking via friends list
In the Steam application, click on VIEW FRIENDS LIST in the lower-right corner.
The blocked user will be listed at the bottom of your friends list in orange.
Right-click on the user and select "unblock."
Unblocking via your profile:
From your Steam profile page, select "Friends," and then navigate to the "Blocked Users" tab.
Check the user(s) that you would like to unblock and select "Unblock"