Thanks for your prompt response, cindy-g1.
In addition to IntuitBooks' answer, it's possible that the Mac system doesn't remember the files that you've recently opened. Let's bring them back by changing the preference.
I'll show you how:
Restart your Mac computer and try accessing the company files from the Open Recent menu.
I'd like to share this resource to learn more about navigating QuickBooks Desktop for Mac 2019: QuickBooks Desktop for Mac User's Guide.
If you have follow-up questions, please let me know. I'll be here and ready to help anytime. Have a good one.