Garmin 235 - you need to format the disk

Garmin are diagnosing my problem in slow motion. They’ve had me check the obvious and then recommended a chkdsk program that only runs on Macs. I’m waiting for the next step. 

Thanks.. if they are suggesting running a Chkdsk program, then it is obvious they have NO idea what the problem is.. it is not a "DISK" issues.. it is a USB connectivity issue...  or compatibility between Win 10 latest build and the file system on the watches.... Oh well...  thanks and cheers

Had same problem a few times with Forerunner 15.  Seems as though during the connection process to my computer something gets damaged on the watch and its all downhill from there. Problem starts on a windows 10 box but still a problem if I switch over to a windows 7 box.  At first I can still get data visually by looking at the screen of the watch, but eventually with repeated attempts to download even viewing directly on the watch screen is gone.  About the only option left is to initialize the watch and start anew.  After that my watch works just fine until the next time.  Just had to do it and now it's back to working fine, except all earlier data is gone.  Instructions for initializing your specific watch can be found on the internet.