as already mentioned, ang daming pwedeng rason kung bakit nagkaganon. it could be a simple thing like say expired cookies (just delete cookies for the site and it should download a new one on next visit to the site), IP ban (although unlikely for a porn site to do so), or you need to login to the site to be authorized to view the content (free lang naman gumawa account sa xvideos last I checked). it could also be something done on your local network, say parental/router controls, use of security software (modified hosts file, AV/firewall blocked access to site kasi may nakitang virus, etc etc)
just checked again today, ok naman ang loading ng xvideos site sakin and I can play videos there without any problems