ProSeries database is not accessible. Please make sure the file is accessible and restart ProSeries (Proseries 2021)

We are having a severe issue with the ProSeries 2020 and 2021 editions on a new server. Our old server no longer satisfies the minimum requirements. This is the Admin install of the Network edition of Proseries 2021. The workstation install works fine on the other machines in the network.

Problem Details

After a fresh install and exactly after closing the program and reopening it a second time and beyond, we get an error message saying "ProSeries database is not accessible. Please make sure the file is accessible and restart ProSeries". After closing the modal dialog, the program just exists. See attached screenshot.

We have tried numerous times to uninstall and reinstall the software with no luck. We have also run "ProSeries Update" and the "Repair Updates" tools. These run fine, but they don't solve the problem at all. I have searched other threads in this community forum and found only one topic but the proposed solution to run the Fix update tool didn't help us.

Server Specs

OS: Windows 11 Pro (Also happened on Windows 10 Pro, The OS self-updated to 11 past the incident  date)

CPU: AMD Ryzen 5, 3.9Ghz, 6 cores

RAM: 16Gb

Disk: 383 GB SSD (80GB used) (We plan to add another disk for client files)

Screenshot

Please let us know how to proceed as this is a critical period of the year. Thank you.