Did you run those arcs before the patch that added Taskmaster Gabriel? Because of the way he works, he can't track any arcs that were completed before he was added to the game. He was in the March 20th patch.
Edit: His wiki link.
That sounds like it could be the problem....anyway to be able to complete those mishs with him?
The End is Near
Yup, just go to Ouro and run the arcs that he lists as incomplete. I ran into the same issue when he was added to the game. For Max's arc, you just need to run his final mission.
Kyle Al'Mordu - Lvl 50 MA/SR Scrap
Fusion Force!
TRIUMPH
I literally just finished my Flashbacks yesterday. I had finished all o'em with a normal play-through before he was added, then had to Flashback and run'em. I didn't have any problems with the Flashbacks, so it should work for you.
"Champion (the Community Server... or GTFO) is like a small town where everyone knows each other's names, for better or worse." -kojirodensetsu.
"If all you have is a hammer, everything looks like a nail." - Maslow's Hammer
I went through all of the arcs in DA, last contact was taskmaster Gabriel. He claims I haven't finished 3 arcs (Heather Thompson, Mu and Praetor Duncan)and Max's final story. I did these already and they are starred when I go to oro to attempt them again. I even ran Max's solo for the third time. They just don't complete for Gabriel. Also, they are starred showing completed in oro, but the color of the mishs remain blue and not gold. Did I miss something somewhere?
The End is Near