Here is the solution as posted on BG:
After discussing a few things with various GMs, one suggested that acquiring the Moggiebag does not necessarily complete the event quest, and that if "loose ends" are left open, the NPCs involved will not go about their normal business.
Turns out I just needed to go back to Kazham and talk to Jakoh again to get a happy 8th anniversary message from her. After that, Maat started functioning normally, and I got the CS for my Black Belt.
Anyway, make sure you talk to each letter NPC TWICE, even after getting the letter key item from them, or the Adventurer Appreciation quest is not considered "complete", even if you have already turned in all six letters and acquired the Moggiebag.