They have pretty clearly enabled Akamai's location-based blacklisting. Note the error message above matches Akamai's documentation for blocked/blacklisted IP's. There's speculation they are doing this out of security concerns (possible account compromises/hijacking), or perhaps tax/regulation concerns (by selling tickets outside their markets). You can get around it by going through a VPN/tunnel that uses US-based IP addresses.
https://community.akamai.com/custome...language=en_US
It's also possible the address space you are using has a poor reputation score. But given the widespread reports, it's seems pretty clear WN is simply using location-based blocks. You can check IP address reputation score and whether it's blacklisted here --
https://www.akamai.com/us/en/clientrep-lookup/