I am using an OfflineMapTask to generate a .mmpk file to load with a MobileMapPackage. I want to have a map with just the BasemapImageryWithLabelsVector basemap, but from it's description, that is the same as the Living Atlas webmap at https://www.arcgis.com/home/item.html?id=28f49811a6974659988fd279de5ce39f. When I use this itemId in the OfflineMapTask, it appears to generate slowly, only getting to about 17% in 2 minutes, and then it jumps up to 100%. The mmpk only ends up being about 600 KB and nothing is displayed when it is loaded with the MobileMapPackage.
Now, my code works for content that I have in my ArcGIS Online portal, but apparently not for any of the public ones from the Living Atlas. Does this mean I just need to make my own portal item for this map, or am I missing something?