This might be just me, but putting this out there in case it isn't.
My one self-published book has been selling steadily since I released it in March, and while there have been occasions when it's stopped selling for maybe a day or two days, this is the first time it's literally screeched to a halt right at the start of a new month.
That might not be enough to draw any conclusions, but, surprised at zero sales with a book that sells so reliably and steadily, I checked my AMS UK reports (I've given up doing ads on Amazon US and, besides, nearly all my sales are in the UK) and they reported at least one sale of a paperback, and no ebooks.
But when I go to KDP and click on 'reports', it tells me two ebooks have sold - but no paperbacks.
My book's rank has plummeted as if there have been no sales. Book Report also acts as if there have been no sales, even after refreshing the data.
I can't make sense of it. Hopefully it's just a temporary glitch.