Is OpenVPN interoperable with PPTP?

No.

Description: The Point-to-Point Tunneling Protocol (PPTP) is an obsolete method for implementing virtual private networks. PPTP has many well known security issues.  Microsoft Windows operating systems still come with native support for PPTP VPNs, but we discourage the use of PPTP.

OpenVPN uses its own open-source protocol, which is not compatible with PPTP.  OpenVPN Connect for Windows is a client implementation provided by OpenVPN, Inc., which you can obtain here:

https://openvpn.net/client-connect-vpn-for-windows/

In addition there are community version OpenVPN clients for Windows.

If you have additional questions please submit a ticket.