PC will not mount my GPSMAP 66st after TopoActive EU 2021.10 install

I have just used Garmin Express to install the latst TopoActive EU 2021.10 map. The installation was completed normally and Express confirmed that I had the latest update. I ejected the device, then booted it up - the TopoActive maps were both installed okay and render normally on the screen.

However when I plug the 66st into my Win 10 PC, the device is not mounted and can't be accessed by File Explorer.

I have tried to fix this - I have installed latest USB drivers and tried the Forced USB Mass Storage Mode steps several times without success. I have tried two Garmin cables and different USB ports. What else should I try?

  • Yes I tried rebooting to no avail. As the device itself boots up normally and displays the updated TopoActive map, I tried it in a different computer. The first PC is running BC 4.7.3, the second one is still on the last stable version 4.6.2. The good news is that the device and its card were visible to the PC and file manager as usual. 

    On opening BC, I got this click through error message (my 66st is running the latest firmware 7.20):


    The new TopoActive maps were read into BC and displayed normally. All mapping on the card was fine and I could see saved tracks etc as normal. I could not detect what the "reduced functionality" in the error message was, but will test it further.

    I ejected the device/card from BC and the PC, then tried again with the BC 4.6.2 computer and got the same error message.

    After rebooting the original PC running 4.7.3 I tried connecting the device again and as before, this would not mount.

    Any ideas?


  • Nope.  Could simply be that BaseCamp, which isn't under development any more, doesn't work properly with the new'ish devices?

  • To be fair to Garmin, BaseCamp 4.6.2 and 4.7.3 has been working fine with my GPSMAP 66st with almost daily use since I got it over two years ago, so I don't have that particular concern. Overall BC does everything I need it for.

    Over on GPSrChive a number of people have also had issues with this particular map install using Garmin Express: http://www.gpsrchive.com/GPSMAP/GPSMAP%2066/index.htm 

    I have just come back from a walk and the device seems to be behaving completely normally as far as I can tell. For the time being at least I have a PC with BC that I can use to talk to the device for GPX transfer.

  • I have been doing further testing. I opened a 'My PC' folder in Explorer on my original Win 10 PC and plugged the device/mSD in. The two drives were added: the card was quickly loaded and showed the free/available space bar as usual but the for the device drive, the green loading bar kept going and going and going ... I went off for a cup of tea and returned some 15 minutes later to happily find that both the device and the card had appeared in Explorer! In the second PC the time to load was much quicker and the same as normal for both. I later timed the device loading time into Explorer at about 8 minutes. I don't know why it is so slow - this has never happened before.

    I then opened BaseCamp 4.7.3 and got exactly the same click-through error message as before. Both parts of the EU TopoActive 2021.10 map were loaded into BC and were visible as normal. I could exchange GPXs as usual between BC and the device i.e. the original PC is now behaving like the second one.

    I then opened Garmin Express which synched with the device okay and I get a message telling me to update the maps to version TopoActive Europe 2021.10 even though that version is the one currently installed!

    I am wondering whether to risk re-installing it again or simply delete the two maps as I don't need them right now.

  • Garmin product support just told me that:

    "Yes this is a known issue and is currently being worked on. Currently it is reported that TopoActive Europe 2021.10 is producing this error in Basecamp but the device still works normally with Basecamp.

    Unfortunately there is not currently a work around to keep the error message from appearing but it is reported that you are still able to use the device like normal despite the error appearing. I will get you added to the report so that when it is resolved we can let you know.

    Please let us know if you notice that you are unable to still use the device like normal with Basecamp."

  • Thanks for sharing.

    Interestingly, I was supposed to update Topo Active maps on my Oregon 750t very soon having been nagged to do so for the last good few weeks (or months?) and I can see that this map is no longer offered for my device as of today's morning. Perhaps coincidence...

  • Someone in the Netherlands has found out what the problem is see: https://forum.gps.nl/viewtopic.php?f=109&p=455363. Garmin know all about this, it should be an easy fix and hopefully a new map should be available very soon. 

  • Garmin Product Support emailed me to say that the updated TopoActive map was ready to install.

    I had already deleted the two TopoActive img files. The new map files installed uneventfully using GEx. These work fine on my 66st and after being loaded into the BC cache, work fine on BaseCamp too and the connection error has now disappeared, so everything appears to be back to normal.

  • Thanks for the heads up.

    Yes, my GE started reporting this map available to download again:

    I cannot understand for the life of me why this particular map/release is so big - previous one fitted nicely on the device and were ~25-30% lighter...