One of the reasons Amazon grew to massive size is its supposed "all about the customer" philosophy.
Make it easy and cheap to buy books ("buy with one-click!"), then introduce other product lines to keep the consumer hooked on an ever-expanding range of easy-to-acquire merchandise.
Enter VPNs, or virtual private networks. These allow users to surf the web with some degree of privacy because the users' (encrypted) connections only go to the VPN host. In other words, the VPN host's server, not the user's, has the IP address the visited website "sees." As a practical matter, this means when a VPN user visits Google Maps, instead of "starting" with a map of the user's neighborhood (a creepy form of surveillance), the map is either of the entire United States or the city where the VPN host has its server, because Google has no idea where the user is.
VPNs allow cookies to be passed to the user's browser, so sites the user visits will still recognize the user on a later visit.
Recently Amazon stopped doing this. Now it doesn't "see" VPN users until they login, and requires two-factor identification to allow them entry to their own accounts (emails are sent to the user with a temporary passcode).*
The reason for this is video streaming. Amazon doesn't want people outside the US to spoof it with stateside VPN host servers.
Unfortunately the company is too technically-challenged to differentiate between a VPN user who wants to stream and a VPN user who just wants to quickly login and buy merch.
Erecting barriers to a quick login, and not "remembering" all the products the user browsed in the last session, is the opposite of the "one click" philosophy. Here's hoping the hubris behind this decision has some effect, however small, on the Bezos bottom line. "I heard Walmart allows VPN visitors and doesn't force them to use two-factor logins!" "Oh, really, I'll shop there because privacy is important to me." Cue jingle.
Naturally there are VPN companies claiming to be Amazon-proof. This plug seems not to realize (or care) that it's not just Prime and streaming that's being blocked by Amazon, but everyday shoppers with VPNs.
*Amazon customer service has confirmed that a "stable IP" address is required to log in to Amazon without 2-factor.