Img not found on kenwood dnx570hd

[BIGBIZ]

Nav seems to not only lost maps but also the garmin buttons as well. says no image available in small letters repeated over and over on screen along with the regular garmin nav warning in small letters as well. nav will not work at all. i have opened the unit and removed the sd card. checked it and it only has 4 files on it. gmapsupp.unl, grmn0.gma,
gtm_nvm.dat, and UnitID.dat . i have no idea where to go from here. any help would be greatly appreciated.

[Youngwombat]

My unit has the same problem I have purchased a second unit cheap will be doing some research into a possible fix my unit is a 2013 and a third one purchased is a 2014 so will be setting them up on a test bench to drill down will let you know
From all my reading due to no image text we can not get to reset the Garmin software so will pull my unit apart to see if there is a hack

have read there is a base map inside mine at least a micro USB have to disassemble unit to get to it
As yet not there but hoping to copy over a replacement base map
Till this is done sit more research on the net as yet not much re hacking a KENWOOD radio with GPS

Are there any experts that have decoded the Kenwood system Garmin any hacks tricks please
Circut diagrams