What error message do you get? Or does the sync show success (on the phone up the white circle around the watch icon closing and turning green)? You can also review (again on the phone app) the Device Sync Audit in Menu » Settings (at the very bottom).
If there are no errors during the syncing, then it means that your device is associated with multiple accounts. It frequently happens for example when you reinstall the application, and inadvertently sign up a new account instead of signing into the original one.
