I have this same problem. I am running a fresh Windows 10 x64 install and I have tried all the steps outlined above. The LaunchBox installer can't detect my .net Core v3.1.19 install. I've tried both x64 and x86 versions. Re-downloaded, uninstalled, reinstalled, "sfc /scannow" and rebooted.
What am I to do? I've paid for the lifetime version and I would very much like to use this software.