Assegnate 5 su 5 stelle

<add 20211109>
Thanks for the reply, I tried based on your reply and finally got it fixed.

Are the add-ons lost? → NO
Are the add-ons enabled? → YES
Reinstalled add-ons → disabled after reboot ( not changed)

Finally, I once disabled the add-on, and then enabled it again, so that it was enabled even after restarting thunderbird.

<original>
In thunderbird91, this can change the icon at the time I add the add-on, but when I restart thunderbird, it will go back to the default black and white icon.
Very disappointing.

Questa recensione riguarda una versione precedente (1.0.4) del componente aggiuntivo. 

Have you checked whether the add-on is still enabled/installed after restarting thunderbird? There's a bug with thunderbird (not the add-on mind you!) that it removes add-ons after a restart of the program.
Re-adding the add-on usually fixes this.

Edit: good to see you got it fixed!