Reformated the micro sd and installed open source map. I can see this in Basecamp with handset connected via cable to PC but not on the handset itself. The name of the map is not appearing in map set up. Looks as if unit is not reading/displaying the SD but how can this be? Is there something simple I am missing?
My experience is more with Edge devices, but...
Assuming BaseCamp is not reading maps locally off the PC, and is actually reading them from the device...
If the card is in the Etrex, and the map is visible on the PC when it's connected, then that tells us the etrex is able to read the card, and offer up the contents as a card-reader.
In Windows Explorer, can you see the SD card and view it's contents when the Etrex is plugged in?
If the card is visible in Windows, but map can't be seen on the device itself, then it's a issue with the device not recognizing the specific file, rather than an issue with it not recognizing the card.
Off the top of my head:
Is the file named incorrectly?
Is it in the wrong location?