Here are my settings for the Callout:
And when I go to the Positions settings there is nothing there for Stack:
It has worked before though. I remember seeing Callouts stacked in a previous project. This one is using a Map Series. Would that make any difference??
No problem! I'm glad it worked out. Labelling is tricky as there are too many variables to consider! Maplex is another one of those things that throws me for a loop all the time.