It should be working. What are the symptoms of this issue? What is happening?

When I go to the websit https://addons.mozilla.org/en-US/firefox/addon/private-relay/ the 'Add to Firefox" is grayed out and it says "To find add-on compatible with Firefox . . ." Note that I have signed into my account at this point. I have tried it with Firefox beta and with Firefox Nightly.

That Extension is for desktop Firefox as it does not say it is compatible with Android Firefox on https://addons.mozilla.org/firefox/addon/private-relay/versions/ A search for Relay in the Extensions for Android Firefox section does not have a result for Firefox Relay https://addons.mozilla.org/android/search/?q=Relay on FAQ in https://relay.firefox.com/ <blockquote>Can I use Relay on other browsers or my mobile device? Yes, you can generate ⁨Relay⁩ masks on other browsers or mobile devices simply by logging in to your ⁨Relay⁩ dashboard.</blockquote> Also since you are using one of Mozilla's premium products you should post in the Firefox Relay section https://support.mozilla.org/en-US/ using https://support.mozilla.org/en-US/questions/new/relay/form as this section you posted thread in is for the Android Firefox web browser. https://support.mozilla.org/en-US/kb/how-do-i-contact-support-relay-premium

See also https://blog.mozilla.org/addons/2022/12/15/new-extensions-available-now-on-firefox-for-android-nightly/