I found that used to happen to me as well. It appeared that running the client in full screen was the cause as when I changed it to full screen windowed the issue went away. The easiest way to get windowed is alt-enter when in full screen.
Hope this helps
I did a similar thing once, to fix it I had to:
Board my spaceship Travel to Zakuul Exit to Zakuul Option to reset chapter now available
Hope this helps
I ran into something similar the first time I was going through KOTFE. I ended up being able to continue by
- flying to Zakuul on my ship
- exiting my ship
And then the reset button on the mission was enabled. Hit reset and the purple play option was available.
Hope this helps
I've run into issues with resetting a KOTFE mission before. The work around I had to use was use my ship to travel to Zakuul, exit my ship and at that point I could reset the mission
From the 4.0.1 patch notes http://www.swtor.com/patchnotes/10272015/game-update-4.0.1:
Cartel Market
Artifact items purchased from the Cartel Market no longer require Artifact Authorization
I also hit the same issue, so I traveled to Zakuul by ship...and no taxi
Then I saw something...wonderful...the reset mission button was now available!!
So I reset the mission and was away.
Hope this helps.