Well, now I feel stupid for thinking the "Ask A Question" box was for the actual question and not header. For the question above:
I'm generating a MMPK for Explorer for ArcGIS (iOS) using ArcGIS Pro 2.4.1. When the file is imported into Explorer it shows as an "Invalid map" and generates a "Unable to Open Map: Mobile map package version is not supported." when I attempt to open it. Is there an update pending for Explorer for ArcGIS to accept these newer MMPKs or is this a misleading error indicative of a different issue?