I have downloaded a cartridge to the appropriate directory /storage/sdcard0/WhereYouGo/directory , both through my PC and directly using "Firefox Mobile" and "Download All Files". The smartphone shows that the cartridge is indeed there, but every time I try to start WhereYouGo, it gives an error message: "No Wherigo cartridge available". It then tells me to add a cartridge file to the exact directory mentioned above. How can I overcome this problem?