So I have tried all of the things that I could think of, I have used the suggested json that firefox have on their git hub found here: https://github.com/mozilla/policy-templates/blob/v1.9_release/README.md#extensionsettings
I have tried this which is nearly the same as it is given in the document above, this did not work at stopping everything apart from uBlock form being installed. Policy on firefox Ghostery being installed These two images are taken with in two minutes so the policy is applied when installing ghostery.
I have also tried to make it so that the specific addon is set to be able to download through the allowed sites setting. GPO Allowed sites This did not work showing the error. Policy error You would assume that just having this would mean that you would not be able to install addons but I am able to install any addon.
I am not able to find anything apart from things about policypak. Which is completly usless to me.
If you have any suggestions or ideas please let me know.