It is my second run/track/run training session of the week and none of them has been synchronyized in Garmin Connect.
The manual upload of the FIT file fails as well.
The upload of the FIT file in Strava works without any issue so I guess the file is not corrupted.
My swim sessions are well synchronized in Garmin Connect.
Last week the synbchronization of run/track/run multi activity training session worked fine.
The watch did not receive any firmware update consequently I guess the problem is on Garmin Connect side.