It looks like there is no silver bullet to make this work.
It comes down to what Android version you are using.
What manufacturer of Phone or Tablet you are using.
If you have a valid Email address setup.
If it is going to be installed on the Internal Memory or a external SD card.
Or what order you install the apps.
Be it both or just the NAVIGON_Europe_v5.5.0_FreshMaps_InApps.apk.
If you have Navigon installed before or not.