There was an update for Mahjong in the Windows Store this afternoon. I installed it, and I went directly to the Mahjong Challenges and was able to complete all the ones for the month of February that didn't load.
Wonderful surprise! Hats off to all who worked on this problem and resolved it. Thank you for your effort, time, and dedication.
Looking forward to playing tomorrow and keeping my fingers crossed, toes too, that the games will run smoothly again. :)