A possible explanation is that the client program is old and supports only certain TLS but the server is expecting higher TLS level.

The solution to this particular problem is to upgrade the client software to the latest version.

A complete uninstall, redownload, and reinstall of the OpenVPN Connect Client should take care of that for you.
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And yet another possible explanation is that there is a blockage in place in a firewall or at the Internet service provider that is blocking or interfering with the TLS handshake in some way.