Are you using this key:

https://github.com/mozilla/policy-templates#websitefilter

I am using Active Directory Group Policy User Configuration-Policies-Administrative Templates-Mozilla/Firefox - Blocked-Websites

I have also Tried Computer Configuration-Policies-Administrative Templates-

I have similar policies for EDGE and Chrome and they both work.

Okay, I see the template here:

• https://github.com/mozilla/policy-templates/blob/master/windows/firefox.admx#L2612
• https://admx.help/?Category=Firefox&Policy=Mozilla.Policies.Firefox::B_WebsiteFilter_Block

In the Windows registry, do your policies show up under either of these keys or are they missing in action?

HKEY_LOCAL_MACHINE\Software\Policies\Mozilla\Firefox\WebsiteFilter\Block\ HKEY_CURRENT_USER\Software\Policies\Mozilla\Firefox\WebsiteFilter\Block\

I see both Keys in my registry

And then under

HKEY_LOCAL_MACHINE\Software\Policies\Mozilla\Firefox\WebsiteFilter\Block\

for example, you have a value such as

1 => *://www.example.com/*

Ref. https://developer.mozilla.org/docs/Mozilla/Add-ons/WebExtensions/Match_patterns

I attached a screen shot of some of the items in the registry

Thank you for the screenshot. The way I read the template documentation,

https://open.spotify.com/

only covers the exact address and you need to add an asterisk to cover all other paths on the server, in other words,

https://open.spotify.com/*

Please refer to:

https://developer.mozilla.org/docs/Mozilla/Add-ons/WebExtensions/Match_patterns

I tried adding the asterix and applying Group Policy but its still not blocking the sites.

I did a basic test of adding to the Registry manually. I ended up needing both the home page path and the asterisk path. This worked, so if you see the policies in the Registry and in about:policies, and they aren't working, that would be puzzling.