Yes, it still has purpose. See https://github.com/kkapsner/CanvasBlocker/issues/349 for further information.

Do you have Privacy Badger installed? I can replicate your issue when both are installed (CB has to be activated first to reproduce it). But please open an issue at https://github.com/kkapsner/CanvasBlocker/issues to discuss your problem in details.

Having some sort of Q&A/wiki page is on my list. If you have specific questions you can always post them at https://github.com/kkapsner/CanvasBlocker/issues

Some sites do not use fingerprinting. That's why the icon is green and no notifications show up. But keep in mind that not all notifications mean that a fingerprint is generated. Also legit use of the APIs can trigger the notification. It's just an indicator that CB did something.

EDIT: great that it works again.

Nothing was done to CanvasBlocke on that date. Last update was on the 6th. But on my end gmail and amazon work fine. Please open an issue on https://github.com/kkapsner/CanvasBlocker/issues with your details (used Browser version, CB version, CB settings, etc.). There we can communicate much better.

The interaction with Firefox's new protection is discussed here: https://github.com/kkapsner/CanvasBlocker/issues/349

In short: the new feature from Mozilla is good but CB still offers additional value.