YouTube no longer allow direct links to a user's account, e.g. https://www.youtube.com/user/xxxxxxxxxxx
This was previously used in member's profiles here, to add your YouTube account if you had one. This has now been changed to the Channel ID, not the User ID.
If you previously had a link in your profile to a YouTube user ID, this will now no longer work and needs to be updated to a channel ID.
Enter just the channel ID, not the full address.