Happened to me when I saw a book on the US site, I wasn’t able to see all reviews, but there was a button to sort-of “apply” to get approved for seeing all of them.
It took five days, then I got this email.
Interestingly, they’re not doing this on the European site, you can still see all reviews there.
There is a lot of stuff where it’s hard to find alternatives to Amazon, but books aren’t really one of those items. Ditch Amazon, support your local book store. Your prime membership pays for Jeff Bezos’ next helicopter ride while his employees are pissing in bottles during shift or just lying around dead somewhere