I'd been trying to update my 2.4.x version of OVPN under Windows 10 to 2.5.7 but it was stalling with the same error as discussed in an earlier thread (
https://forums.openvpn.net/viewtopic.php?t=31235).
I tried the Wireguard deinstall/reinstall but that didn't work but what
did work was updating my Private Internet Access (PIA) Windows app. I thought it might as one option is for it to use OpenVPN. Afterwards the OVPN 2.5.7 install ran without any problems.
So I'm guessing a more general solution for anyone encountering this error is to get hold of a commercial OpenVPN provider's app, install it and then you should have the required driver back in place. No need to have an account with the provider, you just want the app to install driver for you.