If you for whatever reason need an historical version of openvpn connect you are mostly fucked.
but if desperate enough to trust a random site on the internet you can download the binary here.
openvpn-connect-18.104.22.1680_signed.msi x64 only, you can verify the signature at the wayback machine
Don’t forget to check that the sha256 signature matches, it is good practice when downloading random binaries from the internet.
You can download the older 3.1.3 version from a less suspicious link at https://archive.org/details/openvpn-connect-22.214.171.1243_signed
Special thanks to the Totally not suspicious URL for being the only backup version for download before this post was made.