According to zombbo, the developer of Censor Tracker: https://addons.mozilla.org/en-US/firefox/addon/censor-tracker/

I am one of the developers of the Censor Tracker add-on, which is listed on Mozilla’s add-on repository. We recently noticed that our add-on is now unavailable in Russia, despite being developed specifically to circumvent censorship in Russia.

We have not changed any visibility settings, nor have we received any emails regarding this action.

Our Russian users now see this message when they visit the page of Censor Tracker:

*That page is not available in your region.

The page you tried to access is not available in your region.

You may be able to find what you’re looking for in one of the available extensions or themes, or by asking for help on our community forums.*

Can anyone suggest or explain what this is related to? Was there some request from the Russian authorities to make the extension unavailable in Russia or is there some other reason for this decision on Mozilla’s part?