Ulukyn
The button is currently only active if the player is in your friendlist and online.
For technical reasons, we can't activate the invite button for all players if are online, because the client only get the online status of the players in friendlist.
Another option is enabling the invite button all the time, even player not online.
What is the best ?
Not online is probably the best. Since you can /invite SomeoneNotOnline already
---
Tgwaste