Thanks Ken, I had not thought of that...but just tried that and worked in my IIf function, and it worked as desired so good to go!
// Write a script to return a string of the day, month, year from a date field, to show in the pop-up.
// If the InpsDt is null, then display PrevInspDt, otherwise display InspDt
IIf(IsEmpty($feature.InspDt), Text($feature.PrevInspDt, 'MMM D, Y'), Text($feature.InspDt, 'MMM D, Y'))
I think I am getting a little confused about Arcade for labeling and Arcade for expressions in pop-ups.
Would it be correct to say that certain Arcade functions work for popups but don't work in labeling, and vice versa?