We’re currently deploying a hotfix to address this issue, which has been a roadblock for some players.
When the hotfix goes live (soon today), players who are on the quest “The Great Masquerade” when the hotfix is applied will see parts of the event disappear. If that happens to you, please return to Squire Rowe. He will have the gossip option to summon Reginald Windsor, and Windsor will offer the quest again.