I had a similar issue when returning to General Garza's office on Coruscant for a mission debrief (clearly had a mission marker in her office but couldn't enter it).
I solved it by leaving the planet and flying back, could enter after I did...so if you haven't already, I'd try that.
You probably took a priority transport to coruscant. I did that also and it always screws up the mission if you don't go via your ship for some stupid reason. Which is funny because pretty much the only use for priority transport:capital world is for your story quests lol.