It's a bug. The easiest fix is to ask someone to send you an invite when you are in town (or anywhere else that is not a dungeon or skirmish).
As soon as you receive and accept the invite your problem is fixed (until the next time it happens)
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Xael De Armadeon: DC
Xane De Armadeon: CW
Zen De Armadeon: OP
Zohar De Armadeon: TR
Chrion De Armadeon: SW
Gosti Big Belly: GWF
Barney McRustbucket: GF
Lt. Thackeray: HR
Lucius De Armadeon: BD
When this happened to one of my characters, just accepting a group invite didn't fix it. I had to have someone invite me to a group, accept it, and then travel to a different area before leaving the group. Just thought I'd mention this in case just accepting a group invite doesn't work for you.
Comments
As soon as you receive and accept the invite your problem is fixed (until the next time it happens)
Xael De Armadeon: DC
Xane De Armadeon: CW
Zen De Armadeon: OP
Zohar De Armadeon: TR
Chrion De Armadeon: SW
Gosti Big Belly: GWF
Barney McRustbucket: GF
Lt. Thackeray: HR
Lucius De Armadeon: BD
Member of Casual Dailies - XBox