I have a task that says " Have a mastery level 10 in one mana type"
I have now raised 2 mana types to level 10 and have not received my reward.
“no screenshot”
I’ve had this as well. Quite the bummer. Xbox tasks are pretty buggy. @505GamesSupport is well aware of most of the issues, but there’s no harm in telling them again I’m sure 
I believe another console player said getting 3 mana types will complete the task and reward you.
So just keep leveling in the mean time, it should fix itself eventually if what I’ve been told is correct.