I appreciate you for sharing the exact error message and screenshots, Alnada.
Thanks a lot for following the troubleshooting in our knowledge-based articles. I can help you get pointed in the right direction on resolving the "Connection Has Been Lost" error.
This issue is usually caused by incorrect folder permissions, firewall configuration, or internet settings in Windows. Since you've already tried the recommended steps, I suggest contacting our QuickBooks Desktop Customer Care Team. They have the resources and tools such as screen-sharing to help you investigate this further. Please let the representative know what you've tried so far, so we don't recommend the same troubleshooting.
Here's how to reach us:
Open QuickBooks Desktop.
Click Help at the top and choose QuickBooks Desktop Help or press F1 on your keyboard.
On the Have a Question? screen, scroll down and select the QuickBooks support.
Select a topic.
Click the Start a Message button.
I'm sure they will take care of this for you. It's my priority that this is resolved, so please let me know how it goes. I'm cheering you to continued prosperity.