Nav N Go no night mode

I am using ver 8.3.5.193799 and night mode cannot be changed.I set it to automatic, but when I return to that menu it has reverted back to off

Try renaming the folder named Save perhaps?

Thanks, that may have fixed it

No probs.
When you remove, rename or delete the Save folder it resets all iGO8's settings back to default, that's the quickest way to reset everything to see if it fixes the issue.
If you rename the folder you still get to keep any Pins (PIN_V4.sav), custom added POI's (user.upoi) and tracks (.trk) you might have saved over time, just transfer them to the new Save folder.
If the Save folder is deleted that info is lost.