According to the Herald, there's a problem with the /social window that is currently in the process of being addressed.

There is an issue that is causing a delay of the information to be shown in the /social window for some players. We're currently working at resolving the delay and we appreciate your patience during this time. In the meanwhile, if you would like to see who is online in your guild or alliance, please use the following slash commands:

/gc who - Lists guild members who are currently online.

/gc who alliance - Lists alliance members who are currently online.