Mate asking CA Certificate for VPN connection at password mode

Hi everyone. I installed ubuntu mate 20.04 and I need to set up a VPN client connection. When I set type as "password", I still have to fill the option "Ca Certificate", but my server asks only the user and password. How do I do to connect to a VPN without a certificate, using only user and password? Thank you!

My MATE version is 20.04!

Thanks everyone I solved it installing network-manager-pptp

some reading material ... https://openvpn.net/community-resources/static-key-mini-howto/