[BaseCamp] City Nav map missing from BaseCamp

[saddle sore]

I have City Navigator North America NT 2018.3 on my Zumo 550.  It used to
be on my laptop too when I was in BaseCamp.  The other day I created a
route on BaseCamp using that map, then plugged in my 550 and transferred
the route and waypoints from laptop to GPS like I have done countless
times.  This time, when I later went back to the laptop and got into
BaseCamp, the 2018.3 map is no longer listed in the pull down menu box.  It
seems to be gone!  When I checked the map info on the Zumo, it says the
2018.3 is on it though.

Any thoughts as to how the 2018.3 map left my laptop?  (If I can learn what
I might have done wrong, I certainly don't want to do it again).   How can
I get it back into BaseCamp on my laptop so that when I create routes, I
can load them onto the Zumo without recalculations happening -- because the
map on the laptop in BaseCamp no longer matches the 2018.3 map on the GPS
device.

Thanks, Joe Y
western PA

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