The OpenVPN logs found through the pfSense® webGUI at Status > System Logs and the OpenVPN tab show output from the OpenVPN daemon(s) in use, both clients and servers. Messages are shown in the logs for successful connections as well as failures and errors.
If there are no log entries for a server after the process starts, traffic likely is not reaching the OpenVPN daemon. Check the WAN-side firewall rules and the address/port used by the client.
There are several OpenVPN troubleshooting articles found in Troubleshooting.