I have basecamp version 3.2.2 installed on my IMac. I bought the TOPO southern England map for my Dakota 20. The map works on the device but will not show up on basecamp. I've plugged the device in with the map installed and I have tried taking the SD card out and uploading directly into the computer. When I open the SD file and go into the garmin folder I see three files. If I click on GMAPSUPP.IMG I get a warning notice saying the file could not be opened due to no mountable file system! I've run out of ideas, can you help please. 

