Aftermovies

Error type: "Forbidden". Error message: "The referrer https://www.googleapis.com/youtube/v3/search?part=snippet&channelId=&maxResults=30&order=date&type=video&key=AIzaSyBi1ZFe0ZZgSfX4Jrug8RTBK0mIMEPbF_A does not match the referrer restrictions configured on your API key. Please use the API Console to update your key restrictions." Domain: "usageLimits". Reason: "ipRefererBlocked".

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

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