Youtube has changed their URL scheme for profiles/channels so the current setup is invalid
it is no longer: https://www.youtube.com/user/namehere/
it is now: https://www.youtube.com/c/channelnamehere
for example this is my channel's URL: https://www.youtube.com/c/Gamerdevils
When I put Gamerdevils in the field it outputs it as: https://www.youtube.com/user/Gamerdevils and says it doesn't exist.
Just a heads up, thought the admin would like to know about this slight oversight.