Hello, @tring2.

When converting your QuickBooks Desktop company file, oftentimes you'll encounter an error. To help us determine the right resolution for the error that you've received, kindly provide the following information:

• What is the exact error message that you've received?
• In which phase of the conversion process are you getting the error?

In the meantime, you can performed these steps:

1. Open your QuickBooks Desktop, press F2 on your keyboard. 
2. Copy the Location of your File Information. 
3. Close your QuickBooks Desktop (Alt + F4). 
4. Go to your C:\ drive in your Windows and add the file in there.
5. Open your QuickBooks Desktop again. Go to the File menu and select Open or Restore Company.
6. Open the saved file from the new location and try to export the file again.

Once completed, you can start the export the exporting process. You can follow the steps shared by @Fiat Lux - ASIA in this thread. You can read through this article to learn more about the step-by-step process: Move your QuickBooks Desktop file to QuickBooks Online.

Also, I'm adding these articles as additional information about the exporting process:

• How to fix errors when converting from QuickBooks Desktop to QuickBooks Online
• Common questions about importing data to QuickBooks Online

Feel free to get back to us here if you have other questions or concerns. The Community and I are always here to help.