In the current DMD2 version the app will try to load only maps for the country where you are at the moment.
This can be changed, in the same screen where you download maps, after you download any map, there is a “Always Load” button right next to the download button.
If you enable the “Always Load” it will, as the name indicates, always load that map.
If even after this a map is missing then you need to delete it and download again as it is probably corrupted.
For the next big DMD2 we changed this. EVERYTHING about the map layers is configurable so you will need to enable / disable EVERYTHING you want on the map, this goes for the offline map source, online maps or any other layer.