Hi,
when you create a training in garmin connect with a %-sign in the training title like "5min 127%", then the training could not be uploaded to a device. In my case a garmin edge 1000.
without the %-sign no problem.
Would be helpful to have a hint, that %-signs are not allow or just disallow %-signs
Or, even better, figure out what is the problem with the %-sign and fix the issue