ZipCloud will backup your files once per day, if you have added a new file or amended an existing file it will be backed up when your application is scheduled to run. You can however backup a file immediately by dragging a file onto the application or clicking 'backup now'.
Please ensure that the file is selected in the 'backup selection' tab located in 'backup settings'
ZipCloud will track that user anyway and will ensure that you are credited accordingly. If a friend receives multiple invitations from different users, the most recently clicked invitation will get the credit.