Just for the record, updating to 8.1 will not fix this problem. I have 8.1 on my system with all of the most recent security patches and updates applied and Daily Challenges were working fine on it until around April 1st when this game and Minesweeper and probably others no longer automatically log users in to their Xbox live account (or even allow them to manually log in) which makes Daily Challenges inaccessible.
I have been told that the developers are not able to reproduce this very real problem which doesn't give me a lot of hope this will ever get fixed. In any case, still waiting...