YouTube is a little complicated in terms of the various URLs your channel is associated with. YouTube gives its users both a channel URL and a user URL - and they are different. At this point, our system only recognizes the channel URL.
Examples of YouTube Channel URL (Our System Can Recognize)
Example of YouTube User URLs (Our System Cannot Recognize)
If you have a hard time finding a channel URL, please use the 3rd party tool to find it (one tool you can use is https://commentpicker.com/youtube-channel-id.php ).