Me too, there is an issue in the iOS forum for the one which use firmware 2.9. Not sure how it is related. I try to convert the fit file, nothing help. I have the issue if I use Garmin Express, Manual upload or Connect iOs app. What is strange is if I try to import the same file in Strava or SportTracks, no issues.
Yup, my strava works like a charm. So I'm sure it is Garmin's server issue. The problem is there is no announcement regarding this. It make me wonder if they are working on it. It is taking too long.