I couldn’t view the video on Firefox (possibly due to one or more of the gazillion extensions I have installed - I didn’t use safe-mode). However, I could view it on Falkon browser. It ran quite a lengthy ad before displaying the video, so my guess is that the topic starter’s ad-blocker on their router is the culprit.
A possible fix could be for @gnuorder to open Firefox’s settings (about:preferences in the address bar), search for DNS (or select the Privacy & Security section on the left of screen) & change the DNS over HTTPS settings from Default Protection to Increased or Max Protection, so that Firefox uses Cloudflare or NextDNS instead of the router’s DNS.