Hi there,
Welcome back to the Community. I'll be happy to help you with figuring out why you're unable to use projects in the Desktop app.
First, let's start by troubleshoooting the desktop to app. You can by clicking Help, and then Reset App Data. This step will help us clear out the stored program files which impacts and causes issues in the program.
If these steps won't work, you'll have to uninstall and reinstall the QBO application. Here's the link to reinstall the app: https://quickbooks.intuit.com/apps/. Scroll down to the Get the QuickBooks Mac or Windows App section, and then click the Free Download button. Give this a try and let me know how you make out. I'll be here in case you need further assistance.
