Why isn't DialogChoiceSelected working?

The following script stopped working in anything other that studio mode:

print("Script Loaded")
script.Parent.DialogChoiceSelected:connect(function(player,choice)
	print("Pressed")	
	if choice.Name == "Accept" then
		print("Starting")
		_G.addQuestToPlayer(player,QuestName,20)
		print("Ended")
	end
end)

It prints "Script Loaded" but it doesn't print "Pressed" or anything else. It's in a Server Side script in the workspace with filtering enabled (experimental mode off). It's parented under a Dialog. I couldn't find anything helpful on the wiki.