Connection Problem

[YoBoY]

When I connect to server - client connected successfuly but after 3 or 5 seconds it switchs off and all what i can see in Server Log it is:
[17.10.09 0:10:51] Login <login>: 127.0.0.1
[17.10.09 0:10:54] Disconnect: 127.0.0.1
I don't know what to do , i have no ideas , can someone help me ? :oops:

[Hitman]

Which Operating System do you use to test it?