I'd be glad to help you get past this error so you can settle the supplier's outstanding in QuickBooks Desktop, indikes.
I appreciate the screenshot you've provided and performing some troubleshooting steps beforehand.
There are possible reasons behind the QuickBooks Error Connection Has Been Lost. Among these are:
- QuickBooks is not up-to-date.
- Network connectivity issue.
- The folder, where the QBW file is saved, needs additional permission.
- Anti-Virus or firewall is interfering with QuickBooks.
- Power saving options are enabled.
- The Company file is damaged (corrupted).
If you have stored the QBW file on another computer (the one that hosts the file), check if that computer is still attached over the network. The program should remain connected to avoid getting this error.
After that, let's update your QuickBooks Desktop to its latest release. It's a good start when it comes to fixing program-related issues. Here's how:
- Click Help at the top menu bar and select Update QuickBooks Desktop.
- Go to the Update Now tab.
- Select Get Updates to start the download.
- When the download finishes, restart QuickBooks.
- Accept the option to install the new release.

Once, you can restart your QuickBooks Desktop. Closing and opening the QBW file may help in solving the connectivity issue.
However, if the issue persists, I'd suggest following the other troubleshooting steps in this article (process to Step 3): Error message: Connection Has Been Lost.
Kindly update me on how things go or if you continue to get the same results so I can look further into this. I want to make sure this is resolved. Keep safe and have a good one!