This error message is only visible to WordPress admins
Error 403: YouTube Data API v3 has not been used in project 501149559503 before or it is disabled. Enable it by visiting https://console.developers.google.com/apis/api/youtube.googleapis.com/overview?project=501149559503 then retry. If you enabled this API recently, wait a few minutes for the action to propagate to our systems and retry..
Domain code: usageLimits
Reason code: accessNotConfigured
Error: No videos found.
Make sure this is a valid channel ID and that the channel has videos available on youtube.com.