Error type: "Forbidden". Error message: "The authenticated user cannot act on behalf of the specified Google account." Domain: "youtube.common". Reason: "accountDelegationForbidden".

Did you added your own Google API key? Look at the help.

Check in YouTube if the id UC4L8nuy8ZujXKGe9R0T3JHg belongs to a channelid. Check the FAQ of the plugin or send error messages to support.