I am also having this issue. I'm a level 22 Sith Inquisitor on Dromund Kaas (Server: Ebon Hawke). I've also submitted a ticket (# 23043516) to try and git this issue fixed. Note: My character was made way before the 4.0 patch (hadn't played in a while and started it up again). I've completed all known quests that I could see but, alas, I can't find my next story mission nor do I remember the mission I last completed.