@leocg Im on Win10, using MS Defender. It would make no sense MS to block their own website (also other browsers can open it). I didnt mess with firewall either.
Anyway - there is still no official fix for video problem or really slow system tabs (settings, news feed), even on Dev version. Luckly i found solution, it can be downloaded here: https://www.mozilla.org/en-US/firefox/new/