Since I've upgraded to Garmin Express about a month ago, I've only been able to successfully sync my FR910 to Garmin connect 2 or 3 times. The VAST majority of times, Express just says "Sorry, we couldn't sync your device. Please try again."
I've been through every troubleshooting guide there is, I've even completely uninstalled every Garmin product from my computer and re-installed it, but to no avail.
The old Ant+ Agent worked perfectly every time. Please fix Express to the bare minimum of functionality.