Since updating to GE 6.10 I can no longer launch the app. It quits with the error message 'Cannot connect to the Garmin Express Service.' Running Mac OS 10.14.1 on a 2015 MacBook Pro 15"
I just now discovered that the GarminExpress.dmg file being offered for download has been updated to 6.10.1.0. I installed it, and it worked! I had been having the same issue described by others since roughly the first of the month.
Garmin rolled out Garmin Express v6.10.1 for the Mac today. If you would like to update to the latest version, please visit the ‘About Garmin Express’ page from the Garmin Express Menu and select “Check for Updates to Express.” This version includes the following changes:
Resolved a bug introduced with 6.10.0 that would cause users to crash on launch.
Please Note: Any user who is already affected by this crash will have to downloaded the newest version of Express from the website or by clicking this link: Garmin Express 6.10.1
Thank you Garmin. Downloading Garmin Express Version 6.10.1.0 is now working for me. Unfortunately I spent hours trying this week to get Garmin Express to work on my MacBook.