There are 2 main reasons why this can happen
Data within your Garmin file has corrupted and cannot be uploaded to Bunchrides. In the future we will be adding inbuilt tools that will identify and remove corrupted data.
If your Garmin has no memory remaining to store new files, some Garmin models will overwrite older files, however the newest file (Ride activity) will be empty, only the file name will be present.
A good way to identify "Empty" field is to view the file by mounting your Garmin device, the same way you mount an external hard drive to your computer.
Depending on the Garmin model, the .fit files (The native garmin format) are allocated under the "Activities" folder and will usually have "Zero" bytes