Have an active YouTube channel, but you made your channel hidden in the past? You should probably make it visible.
YouTube is starting to close YouTube Channels which are currently 'hidden' or invisible from view. With the ability to hide channels no longer active, any channel that is currently hidden will eventually be closed (if it hasn't been already).
The only options here are to either make your channel publicly visible again, or to close the channel. If you have a hidden channel and aren't sure how to change this, read through this help article.