For more information, i have this message in console :
[SM] Changed cvar "sv_password" to "test".
08/29/2017 - 18:25
7: [basecommands.smx] "Console<0>" changed cvar (cvar "sv_password") (value "test")
Cannot require sv_password when server is already reserved or clients connected!
but the command work when server is empty, that is why i tried before by kick all players with a .cfg