HBO Max has changed its name twice in three years, to Max in 2023 and back to HBO Max in 2025, and its map has changed with it. The service now covers the United States, most of Latin America, most of Europe and a growing part of Asia-Pacific, with different libraries in each, and it is absent from a few large markets: in Canada, HBO's programming belongs to Crave, and in the UK it ran through Sky until the service's own launch there.
What you see depends on the country of your connection and, for some things, your subscription's country. The US library is the largest and is where the sport and the full Discovery catalogue sit; the European versions carry the HBO series and local productions with regional gaps.
The service checks addresses and shows a message that it is not available in your region when it recognises a VPN or a datacenter. Another server in the same country usually resolves it; the account is never the thing being blocked.
GhostShield's four US cities give the US library, and the London, Limburg, Milan and Madrid servers reach the European versions where the service runs.