[Fixed]-Youtube not able to play on my django-heroku app. Giving me a mixed content error message

This has nothing to do with Heroku, paid plans or not. It is simply that you are linking to an http resource inside a page that is served by https; since that potentially side steps the man-in-the-middle protection that https gives you, modern browsers forbid it.

The solution is to serve all your dependent scripts via https as well.