Here is the map layout

On the internal memory you can have:

gmapsupp.img

gmapbmap.img

gmapoem.img

gmapprom.img



On sd card, you can only use:

gmapsupp.img

What maps are you trying to use?

The only 2 that you can see are gmapprom.img and gmapprom.img

Where are you putting these maps???

On the SD card it should be in a folder \Garmin

Maybe try a different SD card.

Have you tried open free Garmin maps as a test???

Spoiler: Get a free test topo map here.
[Only registered and activated users can see links. ]