Hello there, @MaryBinSD. I have some troubleshooting steps that you can perform to resolve issues when unable to open a company file in QuickBooks Desktop (QBDT) for Mac.
To start with, let's ensure your QBDT for Mac update to its latest release. Doing this will help install the recent features within the program.
To update QuickBooks, follow these steps:
- From the QuickBooks▼ drop-down menu, select Check for QuickBooks Updates.
- If a newer version is available, select Install Update.
- When prompted, select Install and Relaunch. QuickBooks for Mac automatically opens after the update.
You can also find more options in the article about updating QuickBooks Desktop for Mac.
After that, check the file you want to open is a company file since you can't open other file types.
Once verified, open your company file again.
Additionally, to learn how to manage your books in QuickBooks Desktop for Mac, see this article: QuickBooks for Mac user's guide.
Keep me posted how things go on your end or if there's anything else I can help you with. I'm always around happy to help.