lost data

I would install Garmin Basecamp on your computer and then select install to computer only in Garmin Express (see fig 3), thus has the advantage of examining the map in Basecamp and allows you to examine the maps and free space on your satnav usint the Install Naps option in Basecamp

 

If you can see the maps you want to use in Basecamp you can send them to your satnav using Basecamp's Install Maps, if you can't see the maps you want in Basecamp then download them to computer only (see fig 3 above)