Autoplay video attribute not working

I was playing around with the element of html, and I noticed that it autoplay doesn’t actually work. This is the code:

<video src="" autoplay controls >

and this is the link to the lesson:

I’ve tried loop and controls, and they both work fine. Am I doing something wrong here?
Thank you for your help in advance

In some browsers (e.g. Chrome 70.0) autoplay doesn’t work if no muted attribute is present. -MDN

Autoplay will work on Chrome if the video is muted, you can just add the word muted after autoplay

Autoplay Policy Changes - Google