You can also fix the problem directly on server. All you need to do is to replace the original CrysisDedicatedServer.exe
file with custom one that disables the kick. You can download it here:https://github.com/ccomrade/c1-launcher/releases
Whole check for the same CD key is disabled there. However, validation of CD keys on master server is still active. That means players can still be kicked for invalid CD key, but since GameSpy is dead, literally any
CD key is considered as valid today. Maybe this feature will be useful in future.