This is the first time I tried the Map Series in Arc Pro. I usually use "Data Driven Maps" in ArcMap, I had to re-create our voting precincts for a new polling place application I put together. I created a relate between the precincts and polling places in the gdb. In the map series, the maps are just feature extent for each precinct and I have dynamic text from the related polling place: Address & Location Name, and whether signs are allowed at that location. For most of the maps, the dynamic data from the polling place is displayed on the map. For only some of them, it's blank. I thought maybe those missing the text, for some reason, didn't have a related record, but that doesn't seem to be the case.