The first thing the dealer tech will try is a hard (power) reboot the 730N. You can possibly save yourself the trip and the time by trying this yourself.
( In case you don't know what I mean: )
In the TIPM under your hood is a 30A fuse, number M12, which monitors power to the radio/nav head unit and optional audio amplifier etc. Pull this and wait a few minutes before restoring it and testing the unit.
If you want to try disconnecting the battery, that is another sure route, but it will end up resetting all volatile memory in modules etc throughout the vehicle. Not a big deal, but a localized fuse-pull is less drastic.