It's nice to see you here in the Community, @Paliredell. Let's work together to get rid of the failure message you received and copy your data to another company file.

Based on the failure message you've shared, you need to set up the sales tax and agencies to transfer the data. Then, copy the data again to ensure all the information is included in the backup. Follow the steps below:

1. Go to Taxes, then select Sales tax.
2. Under the Related Tasks list on the right, select Add/edit tax rates and agencies.
3. Select New and choose either a single or a combined tax rate.
4. Enter a name for the tax, the agency you pay, and the percentage for the rate. 
5. Click Save.

For complete details on how to set up your sales tax and configure the settings, see this article: Set up your sales tax in QuickBooks Online.

If the error persists, I recommend contacting our Customer Support Team. They can pull up your account and help you copy the data to another company file.

1. Go to the Help menu, and select Talk to a human.
2. Choose Talk to a human again. 
3. Proceed with, I still need a human.
4. Click the Contact us link.
5. Select either Start messaging or Get a call.

For additional guide while managing your sales tax rates and settings, you can open these articles:

• Edit sales tax rate in QuickBooks Online
• Set up and use automated sales tax in QuickBooks Online

 Keep me posted on how it goes. I'll be happy to help you further. Have a great day ahead.