MyChat Client error #0027: a user with this UIN is not online or the UIN is incorrect (XXX)

Error

Error #0027: a user with this UIN is not online or the UIN is incorrect (XXX)

 

Error description

Impossible to execute a command as a user is disconnected from the server or UIN is incorrect (<=0 or non-integer number).

 

Problem solution

Check that a user you need is online. You can do it in Admin Panel, the section "MyChat Server", "Online users".