When you say, it 'went dark', what do you mean exactly, Nutty?
Do you mean:
(1) The basic contrast of the screen went dark, meaning that the colours did not stand out easily, possibly caused by travelling north with bright sun shining on the device's screen from behind?
(2) That the individual map squares / panes went very dark grey, possibly leaving you with just the bike's position cursor swimming along against a very dark grey background?
When the individual panes went dark grey, did they mosaic along very distinct lines, leaving you with some panes visible and some greyed out, the whole lot eventually greying out completely?
If (1) go to page 11 of owner's manual, Display Settings.
Not got owner's manual to hand? Worry not.
Select Settings > Display > Colour Mode or Brightness. You can also fiddle about with other settings, like automatic timeout.
If (2) report back here.
PS Irrespective, missing turnings and doing U-turns is all part of the bikermate experience. Cheer up, embrace it. Your mates following might think it tedious and you a nob but feck 'em... Or get them to lead, so you can sit at the back on your awesome steed, sucking your teeth and shaking your head in disappointment.
.