I have Manifold 126.96.36.199 installed and licensed on 2 machines (1 x Intel Xeon and 1 x AMD Ryzen) - both running Windows 10 Enterprise for Virtual Desktops (release 1903).
On both machines, have recently started getting "unknown error" when trying to start any of the Edge versions I have downloaded: 188.8.131.52, 184.108.40.206, 220.127.116.11.
It is "ext.dll" in the M9 Edge versions that causes the error. Note that the M9 Edge versions listed above have an ext.dll that is ~60-70 MB, vs 91.8 MB for the installed 18.104.22.168 version.
However, as nothing changed with the Manifold installation (or the Edge version folder) to trigger the error when starting the Edge version (they were working fine) - I'm thinking that something with Windows on these machines is causing the issue. What exactly, I don't know.