We've received multiple reports of users being banned from multiple servers.

You are not banned from the game.

The Fastpath servers are a known issue throughout multiple Source Mod communities. They have found a way to 'spoof' multiple servers in the server browser which all lead to a single server.

Recently, they've begun banning people indiscriminately. If you find yourself banned from multiple servers this is likely what has happened.

The developers are looking for ways to identify and prevent them from spoofing the server browser.

For now, you should be able to stick to non Fastpath related servers, including:
Flat Earth, House of Rum, Cannabis Club, Hammerclan, m0o, and others.