Just start Crysis, try to connect to one of these servers, wait for the kick and open Game.log to see the reason.
There are many reasons why servers may kick you. For example, some servers run file check. It's possible that your Crysis installation is somehow corrupted. Always use legit Crysis from GOG/Steam/Origin to avoid this issue. Another possible reason is that some servers ban players by their IP address. IPv4 internet is simply broken due to address shortage and heavy use of NATs all over the place. Therefore, it's easily possible that multiple independent players have the same IP address. Especially in games with a lot of active players, which is not our case, but it's still possible that you share IP address with some banned cheater for example. In this case, you can try to ask server admins to do something with it. However, you must first check the kick reason.