I had solved the issue by the following steps:
1. Plug in Forerunner305 and Sync it. You will get error message. Don't bother.
2. Move C:\ProgramData\Garmin\CoreService\Devices\3823510770\FitnessHistory to Desktop
3. Unplug Forerunner305.
4. Delete all the History by the Garmin's menu.
5. Plug in Forerunner305 and Sync it. Sync will be successfull.
6. Go https://connect.garmin.com/modern/
7. Click the + sign on upper right corner-Upload Your Activities-Manual Upload.
8. Go to your Desktop\FitnessHistory. Drag and drop all files which are not in your Activities. You can drag&drop all together.
:cool:
