.GPSMap 64 s not showing in Basecamp, and unable to copy back Garmin file to device.

Basecamp and other Garmin software wasn't recognizing my GPSMap 64s even though I could see it in the Finder on my Macbook Air.  I copied the Garmin file from my GPS 64s to my Mac desktop, then deleted file from the GPS. I then tried to recopy it back to the GPSMap 64s but I get anError message "file to big. need to free up 1.38 GB" even though there is nothing showing on in the Finder/Garmin. Waypoints still show on the GPS but my maps are gone. I now have a useless device.  Any suggestions?