Welcome to the Community space, @Webbersco.

Let’s resolve the error you have with QB for Mac. First, make sure that your QuickBooks for Mac 2019 is updated to its latest release. This is to make sure that you have the latest features and fixes. See this update QuickBooks for Mac to the latest release article for more information.

Then, run the Verify and Rebuild Utility tool can help you fix this. The Verify Data can initially identify any data issues within your company file. Then, the Rebuild tool will self-resolve it.

1. Go to the File menu.

2. Select Utilities and Verify Data.

3. Click OK if you see QuickBooks detected no problem with your data and continue using your file.

4. If Verify finds an issue with your data, you’ll be prompted to Rebuild Now or View Errors.

5. Hit Close.

Once done, run the Rebuild Data utility tool to make sure there is no problem with your file. To do that, follow the steps below:

1. Go to the File menu.

2. Select Utilities, then Rebuild Data.

3. Click OK on the QuickBooks Information window. 

4. Follow the prompt to save a backup.

5. Hit OK when you see Rebuild has completed.

For detailed steps, visit this article: Verify and rebuild data in QuickBooks Desktop for Mac.

However, if the issue persists I recommend reaching out to our Customer Support, as they have the tools to pull up your account in a secure environment and to determine what causes this error. 

Also, you can visit this user guide for additional reference while working on your QuickBooks Account: QuickBooks Desktop Mac 2020 User’s Guide. 

That should get you pointed in the right direction. Please touch base with me here if you need anything else, I’ll be more than happy to help you out. Thanks for dropping by, I’ll keep an eye out for your response.