620 Won't sync

Possible solution

After I updated a new Garmin nuvi 2595 LMT, it Garmin Connect no longer recognizes my Garmin 620. I have uninstalled and reinstalled, I have moved the stick to different ports, the 620 won't upload activities.

I had the same problem when I tried to update my 3590. I found this page useful and the device is now recognised and starting to update:

http://support.garmin.com/support/searchSupport/case.faces?supportPage=Communicator%20Plugin&caseId=%7B380eda80-ac7a-11e0-d01c-000000000000%7D&locale=en_US

I downloaded the communicator and the web updater, but nothing seemed to work until I followed these instructions for a PC:

Plug device into computer
Open Computer
Double-click the Garmin (dezl, nuvi, or zumo) drive1
Double-click the Garmin folder
Cut and Paste the GarminDevice.xml file to the Desktop
Open Voice folder2 and delete voice files not needed
Unplug the Garmin GPS device from the computer
Allow the GPS device to boot up to the main menu
Plug GPS device back into computer
Run the Garmin application again to see if the GPS device is recognized

(if you have a Mac, there are instructions on the page).

Hope this helps.