If new movies are added to a project locally that have not been uploaded to the clould or visa versa you will see a warning that the project needs to be synced. You then need to sync the clould and local versions.
2. The Cloud sync button with the red badge on its top right corner indicates that the project needs to be synced.
3. Click on the Cloud sync button.
The files will start to upload/download and you will see the upload/download progress indicator.
If you need to you can Cancel or Retry the upload or download. See the section Uploading a project to the cloud which shows how to Retry and Cancel.