I've been using keepa.com for years and really like it, but the add-on doesn't appear to work, at least out of the box. Reading some comments it seems I might need to lower some security feature for it to function but none of the things I tried worked.
If the add-on needs extra steps to actually work, that should be mentioned on its front page and/or app settings!
Also, I'd expect at least clicking the add-on icon while I'm on a product page would go to Keepa's pricing history on that product at least, but it just loads my tracking list.
So, right now, the add-on has no use at all for me, unfortunately.

They claim that they support amazon.com.br, but they don't! Fake news.
The first message you get is: "Keepa can sadly no longer update product data for Amazon.com.br"

As promised while emailing Keepa customer service, here is your 1 star review. Your refund policy is antiquated and set up in such a way that makes it appear as if you're only in it for the money. Submitted a request for refund the day after funds were pulled from my account. Most organizations allow for a 10 to 14 day refund request window.

I never use this add on and forgot to log in to cancel the yearly subscription I was automatically enrolled in when signing up.

Seems legit shady.

In response: Horrible response. "Oh your not going to use our product for the upcoming year you paid for it (mistakenly), too bad, we're keeping your money." Enjoy your 1 star.

Non funziona più!

役にたってない