If you ever need to place an IFD5XX/4XX Series Navigator into maintenance mode you can accomplish by either selecting the Download Logs LSK from the AUX>SYS>Status Software Page or from the AUX>SYS> Status Databases Page (Example Below).
If the Download Logs or Update Databases selection is not populated (Example Below) this means the IFD5XX does not have GPS Position and does not know it is on the ground. This is a normal safety precaution that prevents the IFD from going into the maintenance mode while in flight.
This often occurs when the aircraft is inside a hangar and cannot lock into the satellites. You can either take the aircraft outside and allow it to achieve SBAS GPS.
Or, with the IFD powered down, insert a FAT32 Formatted USB stick into the USB slot and power up the IFD. The IFD queries the USB port for a drive and once it detects it, it will assume that interaction with the maintenance mode pages is required.
This will allow you to interact with the Maintenance Menus.