I did a run on my Garmin Forerunner 165, but he doesnt sync it to garmin connect...
Try syncing over the USB cable to a computer with Garmin Express. If it does not help, try importing the corresponding FIT file manually. If you get an error, post the zipped file here, and a friendly fellow user may try to fix the broken file.
How Do I Manually Upload an Activity I Recorded to Garmin Connect? | Garmin Customer Support
To help minimize the occurrence of corrupt fit files sync your device then remove all activity fit files from your Garmin device using these directions - Removing Recorded Activities on a Garmin Fitness Device