Hi,
Thank you for your feedback!
That's because this is related to an issue with an expired certificate in Firefox, causing ALL add-ons to be turned off.
Firefox has now pushed a fix for this, which should be installed automatically for you. You can find more information on it here: https://blog.mozilla.org/addons/2019/05/04/update-regarding-add-ons-in-firefox/

If this issue still exists past Sunday, please reach out to us via support@adblockplus.org!
Thanks,
Jessy
ABP Support Team