Did its server side bug or those players are banned?

[Husarius]

Adding new player to friends list and Profile check results - Failed to connect the server

I have few person which arent online, after checking them Game Profile by right click on thier nick name show up info spat:  Failed to connect the server.

This is serve side bug form few years ago or they are banned?  Sombody occur similar problem and have answer?

I wanna trade with them but they arent online, 6 persons has this issue.

[Leqesai]

Could be a number of different issues. 

In my experience this sort of thing happened most often when I hadn't properly set up my network or I am trying to connect to people who have networks that aren't set up properly.