Alright, so... This extension works *almost* great when it works. I start all my reviews with a 5 star rating, rounded down, as it seems there is more often "useless" 5 star reviews more often than "useless" 1 star reviews.
This one has lost 1 1/2 stars instantly, due to many issues with saying I am signed out when I *just* signed in, and seeming to fail to detect my amazon account at least half the time.
The second issue I have, is, when I am signed in, it seems *unable* to display my current shipments and orders on the extension, without loading the amazon website, despite their being an extension for it, losing it 1 star. It gained 1/2 of this star back though, bringing it to a total of 3/5, due to order notifications working, and at least I can know when it arrived to go check my door/mailbox.
I *can* reccomend this extension for heavy users of amazon who just need to know if their package should have arrived, but for casual users or heavy users who check their shipments obsessively, you would be better off just leaving an amazon tab open, unless notifications are a major draw for you.
I will likely update this review as the extension changes.

Other extensions I have likely to impact results:
Ublock Origin + Custom block lists: Might be responsible for the login issue, but disabling and restarting browser seems to have had no effect