The extension no longer accepts passwords. Most likely it has to do with new firefox update. You enter correct password and instead going to the page you intend(i.e. addons) you get password page again.
I'll also raise an issue on Github

Sadly, today july 29, 2020 firefox updated the browser and this add on is broken now miserable, it won't accept the password you set on new version of firefox :(

thank you

I would like more flexibility, for instance if I only wanted to block browser changes from Firefox to Chrome, or wanted any combination of functions. The browser switch, though, is my priority.

goooood

If you add '?' you can access the addons page, please fix this and it will be perfect and I'll rate 5 stars

o.k.

Great idea, but easily bypassed and causes tabs to constantly reload themselves whenever you switch between them. Not recommended. Just get a site blocker that also features an addons page lock.

As someone else mentioned, there's a delay when you restart the browser which gives you more than enough time to disable the addon...which kind of defeats its purpose. It would be great if you could fix this.

no funciona nada

When I restart the computer and open Mozilla, there is a window of time where the block lags and can be disabled. My son used this to get through to the safety add-ons I have, can you please fix it??

This actually works pretty great. But there is a bug: If you add a ? to the settings or addons page url like about:addons? you get access. Please fix this!
It would be great if it were possible to add URLs that are password protected and not just blocked.