Hello,
There is currently a problem with the guild-chat & alliance-chat that was extended from Guild Masters only to members as well, after the update from today, when we've tried to fix the Guild Masters problem.
If we can't try a new fix for it in the next 1-2 hours you'll have to survive until tomorrow without this chat functions.
We don't want to do another server restart today without trying a new fix, so in the worst case we'll do a server restart tomorrow for either trying out a new fix or roll-back-ing to previous update where the problem was only for Guild Masters, until we have a new fix to try.
Happy leveling!