I am trying to access my Quickbooks Online file using the desktop app version 3.5.2....however it does not open and just hangs

You can uninstall and then reinstall the application to ensure that the program you have in your device isn't corrupted, David. This way, you can utilize the QuickBooks Online Desktop application seamlessly on your computer.

To begin, here's how:

1. Select Start and look for the QuickBooks Online Desktop application.
2. Press and hold (or right-click) on the app, then select Uninstall.

If you're using a Mac OS, please see this page to help you with the process: Uninstall apps on your Mac.

In case the issue persists, we recommend contacting our Live Support so they can assist you in determining the root cause of the problem. This way, they can assist you in setting up your QBO Desktop Application on your device. For more details, please see the Resolve issues with the app section on this page: Download and use the QuickBooks app on your computer.

You can revisit us and leave a comment below if you have other questions about the program. As always, we're ready to extend a helping hand in sorting out your QuickBooks-related inquiries.