On openvpn setups where MD5 is still in use with the SSL certificate, it’s now impossible to connect when you are in Fedora 21.
To allow openvpn client to connect to such VPN using NetworkManager, you need to modify /usr/lib/systemd/system/NetworkManager.service and add the following two lines in [Service] section:
Environment="NSS_HASH_ALG_SUPPORT=+MD5" Environment="OPENSSL_ENABLE_MD5_VERIFY=1"
Restart the service and it will work 😉