On a fresh installation of Windows 10, I found that Youtube was working just fine, but other embedded videos on sites like Twitch and Reddit were not. I thought it had something to do with HTML5 or flash, but as it turns out, it was because I had chosen the wrong version of Windows during the installation process. Choosing Windows Professional N or, basically any N version, results in video issues primarily due to the lack of appropriate codec and DRM support. Even Netflix will very likely not play. This also affects all browsers.