This was a fantastic documentary from TVO (TV Ontario), an Ontario, Canada provincially funded arms length government entity similar to state funded PBS affiliated TV stations in the US.
Its usually because the host site has only signed a limited distribution deal, and the copyright holders have sold or are seeking to see separate distribution deals elsewhere.
I run into this sort of thing regularly when I try to access content like Saturday Night Live broadcasts. There are separate Canadian distribution rights, so I am unable to access the shows that US based consumers can access through their internet access.
If you can't see it because of geo-restrictions , you can usually find a browser extension to fake your location or provide a VPN to get round the issue.
have a google* for "free vpn", "vpn plugin", "anonymous proxy" or similar and you'll soon find instructions.