Telnet closes immediately

When I open a putty telnet window on I entered the requested login and password.
Then the window immediately close.
I’m sure to send the correct credentials.

Does this work for other users?
73s, Martin, DF1DN

Try to use Raw mode in puTTY (or disable Telnet negotiation). Otherwise it is possible that invisible Telnet control characters might be interpreted as part of the username/password.

Thanks, setting telnet negotiation to passive resolved the same issue for me.