Garmin Express vs. Sequoia 15.0.1

P.S.  That's Garmin Express 7.23.0.0

Hey FRED5279

So I was having this same struggle and was starting to lose my mind. Anyway, I figured this out... Here is how you can get this working.

Overview:

1. Ensure Garmin Connect has Full Disk Access Enabled
2. Manually Mount the Device in Mac "Disk Utility"

Steps:

Ensure Garmin Connect has Full Disk Access Enabled

1. In Spotlight (Cmd + Space), open "Privacy & Security"
2. Select "Full Disk Access"
3. Ensure "Garmin Express" is listed and the slider is enabled
   1. If Garmin Express does not show, press the add button and select Garmin Express

Manually Mount the Device in Disk Utility

1. In Spotlight (Cmd + Space), open "Disk Utility"
2. In the sidebar under "External" locate your device (typically named "Garmin") and select it
3. In the top right of the window page, select "Mount"
4. It may take a couple seconds before mounting but once mounted will open Garmin Express.

Absolutely frustrating that Garmin has absolutely 0 documentation on this. But here you go!

Thank you for this.  Is this a one-time procedure, or will manual mounting of GARMIN be required every time a device is connected?

There is another problem that has to be resolved first.  In disk utility, no external volume appears when the nuvi 3950 is connected, even though Sequoia asks to approve connection.   (The device's battery is charging via the connection.)  I finished spending 56 minutes on the phone with an Apple senior support technician as he watched screen share and had me go through various steps with both GPS units, with and without Garmin Express running.  There are communication problems with Garmin devices, and he did all possible on MacOS's side, including safe mode.  The issue is being saved for the Apple engineers so that there will be follow-up, but now it falls to Garmin to start troubleshooting the problem of their GPS devices' compatibility with Sequoia.  

My next step will be to raise the issue with Garmin support, but the age of my GPS devices may not spark their interest.  On the other hand, Apple tells me Garmin needs to  troubleshoot anyway, because all the modern Garmin devices communicate the same way and this communication issue will impact even their newest devices.

In the alternative, I'd have to revert to Sonoma or create a partition just for Garmin Express.

...

As for Garmin support, they started having me go through all the hardware tests that Apple already completed with me with Apple's online screen sharing.  I went along with it until Garmin troubleshooter wanted me to get another computer and also delete everything from the GPS devices.  At that point I asked if they would raise the issue to another support level (the Garmin engineers did a beautiful and quick job on a GPS glitch in the past), but I was informed I was done with troubleshooting, and goodbye.  

Hopefully the communication with Sequoia issue will be resolved through some means so that my devices will be able connect with Express to update firmware and "lifetime" maps.