Sign in to YouTube
Go to the channel you want to unblock
Open the channel page
Click the three dots or More options
Select Unblock user
Refresh the page if needed
If you blocked the channel in a comment, go to YouTube Studio
Open Settings
Go to Community
Find the blocked users list
Remove the channel from the blocked list
If you blocked someone through Google, check your Google account settings
If you cannot find the option, use YouTube on a desktop browser
If the block was done by a parent or school account, ask the account owner to unblock it