This is probably related to the external storage. The map library (osmdroid) needs external storage (a SD card, for example) for the tile cache. If the external storage is not available, the map is shown as a grid.
("external storage" is a term used by Android to refer to any directory without reading/writing restrictions. It includes unprotected areas of the internal memory as well as SD cards)
The external storage won't be available and the map will be shown as a grid in these cases:
- There is not a SD card, or the library cannot identify the SD card. This may happen in very recent versions of Android. I don't have any device running Android 4.4, so I'll need your help to check if this is the case.
- The SD card or the internal memory is full. I cannot help you with this
- The SD card/external storage is not available to any application on the mobile phone because it is mounted by another system. Typically, this happens if you connect the device to a PC using a USB cable. If you are using a USB cable, please, unplug and test again.
I have pending an update of the application from months ago. I really hope to test the new version and push the update during this weekend. Particularly, airports and navaids are now displayed on the map.