It took some time for me to make the extension work in latest firefox version.
Just make sure that tracking protection is disabled for your amazon site or that you are blocking third party cookies from tracker only.
There are different cofiguration that may work if anyone have issues I will keep an eye on this message to help if needed.
I have to say that people from support (firstname.lastname@example.org) replied to my email really fast! THey will aslo help you if you are in trouble.
One of my favourite features are notifications via Telegram, sick!