Incomplete Syncing

Since yesterday, my Vivosmart has only been doing partial syncs with my iphone. At the moment, it only syncs HR, steps, intensity minutes, floors, and calories. It no longer syncs body battery, activities, stress, sleep, or sleep pulse ox. I can see the unsynced data on the vivosmart, but not on the app or on Garmin Connect.

When the iphone app syncs with the Vivosmart, the progress indicator on the phone only moves a little. It doesn't sync the way it normally does, where the progress bar gradually moves around the circle. I don't get an error message after syncing, but it's obviously not syncing much of the data.

I tried un-pairing my watch from my iphone, then re-connecting it, but that didn't help.

Any ideas?