I’d like to know this as well! The user ID provided by YouTube just throws an error. I think it needs the channel ID, but that’s different than a user ID the URL has to contain /channel/. So even the link in the error is wrong, pointing to /user/.
You probably already figured this out but lets just put it here for others searching for this.
It’s in the instructions:
“Identify by: option to select the type you want id to use to identify your channel, your user name or id channel. Shortcode attribute: identify_by; value: username (default) or channelid. (Optional).”
So set in your shortcode identify_by:”channelid” and user:”your_channel_id_here”
Yeah, we did figure it out. Thanks though. This could help others.