OK - is that Best Buy store LOCAL to you?
I only ask because you MAY have received a faulty unit, and return to the store for a working unit would be the best next step.
If this is NOT a local store, and you have a closer Best Buy in your area, that local store MAY exchange a new working unit for you, but I sometimes have had trouble doing that - especially if I don't have the original receipt with me or do not visit the local store very often.
I also have ONE other thing to TEST - which is SETTING and adjusting the volume (and perhaps MUTE) from the MAP screen.
While on the MAP screen, you should see a SPEAKER icon. Tap that icon and additional controls should appear on EACH SIDE of the screen.
the RIGHT side should show the speaker in the middle, with + and - buttons ABOVE and BELOW the speaker. Tap the + and - buttons to see if the level gauge moves up and down, and tap the SPEAKER in the middle to see if the sound MUTES or UNMUTES when you tap it.