Deceptive licensing, dead project (no updates in over a year), and does not play nicely with other privacy enhancing add-ons.

The Addon is dead, no Updates since 2 years, better use Ublock Origin and Privacy Badger

After a while the Disconnect icon turns to a jigsaw icon. That does Firefox incapable to connect any site. I don't know what happens but it's grazy!

goood

It just works

This extensions apparently is not maintained: it hasn't been updated in two years; also, it has some no longer used code, e.g. /data/services.js is no longer used because the data was moved to /data/services.json. Furthermore, Disconnect is rather limited in features compared to uBlock Origin, AdGuard, Adblock/Ablock Plus, etc. Specifically, it uses domain-based filters, so is unable to block site's own tracking. You might as well install a hosts file and/or block third-party cookies and get pretty much the same result as with Disconnect at a fraction of resource use.