Try to use a Microsoft browser; the Win 10 Edge ones. Without excessive modifications; adblockers or elsewise. Else, I have seen a lot of problems reported with "the others".
Also, you may want to try running a default setting on your router; possible you may have QoS, port filtering on either router or the computer firewall that is interfering with the website HTML5 player. Although I don't have specifics as to what these are, or if any special requirements even exist.
sorry the solution is never to use a browser. a company like funiamtion should be able to make service for most common browsers. but yes I've seem to been having problems the last week or so with vids on the site.