If you scroll through to software update in the menu options on the watch, does it offer you the option to install the update?
From what I remember of installing updates on mine, Garmin Express merely loads the update file on the watch for you to then install using the watch's menu option. Perhaps Garmin Express thinks its job is done once it has put the update file on the watch.
When I scroll through to software update in the watch, it says "Go to Garmin Connect to check for updates".
Garmin Connect in my phone says there is a software update available but it does not give me the option to update it.
Garmin Express in my computer says "Your device software is up to date - Version 2.50". The "Check for Updates" link does not change anything.
Reinstalled Garmin Express, same problem.
So it seems that Garmin Express is not able to see that there is an update available, and since this is the only update method, I'm stuck in version 2.50.
I have the same problem with my Garmin Forerunner 620. Garmin Express says 2.60 is up to date, but Garmin Connect says there is a new update 2.70 and I am unable to update it through Garmin Express. Please help! I really want to update this ASAP as one of the mentioned fixes is the failure to transfer the GPS data which my watch is also having the same problem.