I think the problem here is a bit more complicated and nothing to do with Windows 10 updates. It is also nothing to do with previously installing the maps on C:, which is what Express specifically warns against.
I have an old Windows 7 system that took some iterations before I could get my Nuvi maps accessible on a non-C partition. However, I did succeed some years ago and it was working until recently, but now I check again after the 4.7.0 "upgrade" they are no longer visible.
I just started on a clean win-10 system. All my non-licensed maps installed on G: drive and worked as expected. I then used Express to install two maps and neither appeared in Basecamp.
What is evident is that Express thought it knew what it was doing to install for Basecamp. For each map it created a shortcut as a shell .lnk file with a target as the correct folder on my G: drive. I simply removed these and made an NTFS junction so that ProgramData\Maps pointed to G:\Garmin\Maps and Basecamp was happy.
Use of a shell link file does not really work very well when the target is a folder, but all I can think is that, somehow, the way old versions of basecamp worked was that they parsed the file and found the target. Maybe recent version(s) of Basecamp changed the library used to find files and it no longer works that same way. Just guessing, but it did work and now doesn't.
same here as well, on 2 different devices....Garmin-Windows problem.
Works perfectly on both my windows systems, one win10 the other win7, so it's not as simple as saying it's a Garmin-Windows problem.
Just had the same issue with Basecamp 4.7.1, but it is actually caused by Garmin Express. When installing in an alternative location, Express will create a short cut to that location in C:\ProgramData\Garmin\Maps. I found that the shortcut was invalid. So deleted that, made a new shortcut and it works. No need to reinstall or anything.
Quite silly Express is having this issue for so long. Should be a dead simple fix.
Cheers.
(3) Run Garmin Express, select Map Options to then get the Map Options window that allows you to install/reinstall the map to your device
I know this is an old thread but there are no 'Map Options' option to select in the current version of Garmin Express.