Same check, so Maat can't be played by a character who already played a blessing on the check.
If a player plays a blessing on a check BEFORE the roll, and wants to change the check for whatever reason AFTER the roll with Blessing of Maat, can s/he do so, or would that be considered the same check?
wkover is right: Same check, you can't have both cheese and iing on the cake.
You decide before the check if you add dice by a blessing or if you don't and keep the possibility to use Maat.