Intuit recently released QuickBooks for Windows, which is QuickBooks Online in a desktop application. If a customer is having trouble syncing a QuickBooks desktop file, make sure they are not actually using the QuickBooks for Windows app.
At first glance, it looks similar, but after seeing QuickBooks desktop enough, it won't be difficult to recognize the differences. The biggest indicator that someone is using QuickBooks for Windows is if they use the login box shown below. Below the login box is a screenshot of QuickBooks for Windows.
In order to sync a QuickBooks Online file that is being used in QuickBooks for Windows, you may simply follow the normal QuickBooks Online link and sync instructions found here: