The system requirements are the reason why you're having issues when using the app on your Mac OS. Right now, the app currently supports OS X 10.9 (Mavericks), 10.10 (Yosemite), and 10.11 (El Capitan). You can read this article for more information: QuickBooks App for Windows and Mac: General Support.
Using the Quickbooks Online 'desktop' app on a Max (OS X Catalina 10.15.5). The application window is fuzzy and unreadable, like looking at static on an old television.
Hi there, finance58.
I'd like to add some information about your query.
As Apple increases Catalina's security requirements from time to time, our engineers are also doing their best to meet these requirements. For the latest update, we are looking to this compliance and fix this out. This way, you'll be able to use QuickBooks on a Mac (OS X Catalina 10.15.5).
We always value our customers' opinions and take them as consideration. Meanwhile, you may consider checking the links provided by my colleague above for more details about the system requirements.
If you have more something to tell us, please tap our shoulder anytime. We always want to hear from you. I hope you're okay. Keep safe.