I want to stop this from happening to you, @Nonee. I have various solutions. 

Thanks for doing some basic troubleshooting steps before posting here in the Community. The steps you've done are the best starting point to resolve the issue. We can work together to fix the problem that wasn't resolved during the rebuilding process.

To begin, ensure that your QuickBooks Desktop is in the latest release. This way, you always have the latest features and fixes. You can press F2 on your keyboard to see the version you currently use. 

If it's updated and the issue persists, I'd recommend utilizing the File Doctor feature to fix company file issues. I'll show you how: 

1. Download the QuickBooks Tool Hub version (1.5.0.0). 
2. Open the file you downloaded (QuickBooksToolHub.exe).
3. Agree to the terms and conditions. Then follow the on-screen instructions. 
4. Open the tool hub and select Company File Issues.
5. Choose Quick Fix my File.
6. Click OK when done. 

If you see the same error, follow Steps 3 to 5 in this article: Fix company file and network issues with QuickBooks File Doctor.

However, if the problem continues, I'd suggest saving the backup to your local HD, then copying them to the external or cloud drive folder. 

Moreover, check out these articles below on how to back up using Intuit  Data Protect and fix general company file problems in QuickBooks:

• Make a backup with Intuit Data Protect
• What to do if you can't open your company file in QuickBooks Desktop

Lastly, may I ask for a screenshot of the error? This way, I can further investigate the error and provide you with the most suitable solution. 

I'll be waiting for your response. Feel free to leave a message below, and I'll get you back. Keep safe, Nonee.