Garmin Edge 840 does not connect to Garmin Express

This fix worked for me running Monterey OS on an old Mac pc.  You connect the 840 OFF and it starts automatically per 2 above, then do 3. Thanks v much as I spent a lot of time trying to find an answer to why it connect sometimes and not on other occasions, with my Garmin Connect app freezing resulting in my having to force quit it.  

Thank you!!

Here is my experience with Edge 840 on a Macbook Pro M4

Setup:

After several map-auto-update attempts that failed my Edge internal storage got fully filled up to the point it was showing -377Mb of space. Of course, one is not allowed to remove maps directly from device.

The firmware on my device was somewhere around 24th major version that is quite old as of July 2025.

The Garmin Express software couldn't see my device. Garmin Connect on my iPhone, however, could.

Here is how I got out of this situation:

- I've requested a firmware update on my Edge, but when it shown me that "transfer is already in progress" I've forced it to use bluetooth. This way it started to actually show progress, and after only 20 minutes it managed to download a firmware update of sorts and proceed to install it.

- To my surprise, installation of the update require Edge unit to be disconnected from ANY usb cables, even if it provides only charging.

- Even to bigger surprise, the firmware that was installed this way wasn't the latest one. But, new enough so the Edge connected to Garmin Express (if you removed any MTP software that tries to connect from your computer — Google Drive, Dropbox, Androind File Transfer and so on).

- I've seen in Garmin Express that indeed, the storage space is beyond spent. Luckily, it allowed me to delete all the maps from Edge.

- After each operation it requires to reconnect, otherwise it cannot go further, so one manipulation with maps per connection.

- Garmin Express installed maps I've requested, and also installed a firmware update that was a bit newer. 

- After that when I have booted the Edge without connecting it to USB it downloaded and installed what I believe the really latest version of the firmware to this day, version 27.14

Finally, I have my Garmin Edge 840 with newest Garmin maps of Western and Central Europe, and with newest firmware also.

But my journey didn't end there. I like to use a special map for navigation in the Netherlands — it is made from OpenStreetMap data and it gets updated every month. With all the construction work that is happening in the Summer it is rather handy.

Before (in March, to be precise) I was able to connect my Edge to the Macbook and it would show itself as a thumbdrive, where I can just copy gpsmap.img of desired map and be done with it. Now however thumbdrive method doesn't work (I don't know who is to blame here, Garmin or Apple).

So, I needed to install Garmin Basecamp, Garmin MapInstall and Garmin MapManager. Last two come in one .pkg file that is quite outdated, it is from 2022, and I am surprised that it still works.

After installing these, one have to open downloaded map (only in .gmap format, mind you) with MapManager and install it to the special folder that is considered to be Garmin folder of truth on your mac. For me it was inside ~/Library/Applicatio Support/Garmin/Maps/... folder.

When it's done, one can use Garmin Basecamp to have a look on the map. Careful though, one shouldn't have Basecamp running when map installation to the device is ongoing — failures happen.

So, last step was just a breeze — run Garmin MapInstall and politely ask it to install the map we've downloaded and installed to a special magical folder to our device (that is of course must be connected to USB and NOT be in MTP mode).

I wouldn't say that this is the shittiest UX I've seen in my life, but it is a close contender for the first place.

Edit:

Map that was loaded by Garmin MapInstall doesn't show on device! Version of the same map from March that was copied in thumbdrive mode works just fine! It's a joke, not a software

Edit 2:

I have used a Linux laptop to connect to Edge using MTP mode, and copied a map to it directly. It worked.

My MAC with the latest version of express - cannot find my edge 840.  Garmin just told me that it isn’t their problem.  I’m lost at this point.  Suggestions ?