With the newest update for Edge x40 series a different way to communicatie between the Edge and a computer is used, called MTP. macOS has limited support for MTP which can result in a couple of issues. One of them is that only one application may access the device at a single time.
So, if you use Basecamp and that already running when you start Express, Express will not recognize the device. So make sure that there are no other applications running that could try to access the Edge (Basecamp, Android File Transfer are a couple of examples).
I was on lower firmware version when I went to update my maps. After removing old maps it asked me to reboot and install an update which I did. After that I never managed to connect my 840 to express. Tried uninstalling express, rebooting laptop, rebooting edge... no luck Fenix 8 still connects normally.
in a German forum someone posted a workaround, that ist working for me: The Edge is off, Express is off. Connect the Edge via the USB cable to the Mac. The Edge starts up until the USB connection site ist on the screen. Then start Express.
In the meantime I updated to 25.25, but that did not work for other sequences, only as described above. Update on 25.25 described here: Edge 1040 Series Version 25.25 - Pre-Rollout
I have the same problem, brand new Garmin 840, updated the firmware, now it won't connect to my Mac. Tried the workaround stated above, but it doesn't work for me.
