I just spoke with a rep over live chat. This issue is known, but currently unknown as to why it's happening. The only answer I can add to this convo that hasn't been added yet is this from our live chat.

Yes, there was a recent technical issue involving server equipment that affected multiple Primal Data Center Worlds. Although our team has investigated the issue and resolved it, there is a chance that the communication conflicts with regards to the login status of characters on the affected Worlds have not yet been resolved.

Yes, we have recently received multiple similar reports with regards to this specific issue. At this time we may need to wait for the various servers to sync before access to the affected characters may be resolved. Fortunately there is a planned emergency maintenance tonight.