Hi there, BBB11. 

Thank you for posting here on the Community page. I'm here to help you fix this display error on your QuickBooks so you can get back to business.

If the QuickBooks screen appears small, then we need to make some adjustments. You'll need to look at a few settings to correct the screen resolution.

Here's how:

1. Close QuickBooks Desktop.
2. Right-click the QuickBooks icon, then select Properties.
3. Go to the Compatibility tab.
4. Select Disable display scaling on high DPI settings check box. You can also select Change high DPI settings and then Override high DPI scaling behavior.
5. Select Apply, then OK.
6. Open QuickBooks and check to see if the windows are visible.

If the issue persists, please check out this article for more troubleshooting steps to be performed to get this resolve:  Fix screen issues in QuickBooks Desktop.

For future reference, read through this article: Use QuickBooks on multiple screens or in Multi-Monitor mode. It helps you learn about how to enable multiple features and their limitations. 

Feel free to loop me in if you have any QuickBooks questions.  I'm always available here to lend a helping hand.