I've noticed that if you're website is being served over HTTPS, a YouTube video will fail to embed since it's attempted to get the non-https embed resource, and therefore rejects it.
Console error on inspect reads:
Mixed Content: The page at 'https://www.example.com/forums/8917-thread-name-here' was loaded over HTTPS, but requested an insecure resource 'http://www.youtube.com/embed/videoidhere'. This request has been blocked; the content must be served over HTTPS.
I've noticed that if you're website is being served over HTTPS, a YouTube video will fail to embed since it's attempted to get the non-https embed resource, and therefore rejects it.
Console error on inspect reads:
Mixed Content: The page at 'https://www.example.com/forums/8917-thread-name-here' was loaded over HTTPS, but requested an insecure resource 'http://www.youtube.com/embed/videoidhere'. This request has been blocked; the content must be served over HTTPS.