Heath,
A bug was introduced into ArcGIS Pro 2.3 with regard to writing symbol and label definitions for operational layers in a mobile map package, and we did not catch it in our testing. We will release a fix in an upcoming patch for ArcGIS Pro.
Depending on how the Map is being used, if the layer is in a basemap, the layer and labels with render correctly.
Of course if the layer is in a basemap access to the features, ex. Popup, is not possible.
If you do not have another compelling reason to use ArcGIS Pro 2.3, it may be best to wait for the patch.
Sorry for the inconvenience,
Mark