Did you checked the VPN server widget in the dashboard?
Did you used the road warrior configuration or the zentyal to zentyal tunnel?
Did you configured your clients with the correct zentyal "bundles" provided by the webadmin?
Check your vpn server this way:
sudo zs openvpn status # the output should be "RUNNING"
# or
sudo systemctl status openvpn
Checking the UDP listening ports
sudo ss -ulpn | grep openvp
Checking the firewall rules: (Did you tried to create aservice for the udp 1194 port and grant access to it in the Firewall module?)
iptables -L | grep openvpn
Check the openvpn logs here:
# "test" is the name of my openvpn server. Each of them have his own logs.
less /var/log/openvpn/test.log
If you need more info, read about this command:
sudo openvpn --help
Cheers!