probably you have to rename it, it depends on your device and on where you put it
read tutorials about storing maps in devices
these
How to view hidden map folder in 1xxx nuvi series
Garmin Nuvi MapSet format- how to store them in your device
Multiple maps on SD Card
Multiple maps on nuvi 1XXX series
Multi maps on Nuvi 7x0/7x5
Oregon Maps
Multiple maps on 3790 SD Card post 18
here
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