pfSense » pfSense Packages

https://build.openvpn.net/man/openvpn-2.5/openvpn.8.html:

--explicit-exit-notify n

In UDP client mode or point-to-point mode, send server/peer an exit notification if tunnel is restarted or OpenVPN process is exited. In client mode, on exit/restart, this option will tell the server to immediately close its client instance object rather than waiting for a timeout.

The n parameter (default 1 if not present) controls the maximum number of attempts that the client will try to resend the exit notification message.

In UDP server mode, send RESTART control channel command to connected clients. The n parameter (default 1 if not present) controls client behavior. With n = 1 client will attempt to reconnect to the same server, with n = 2 client will advance to the next server.

without this option "Concurrent connections" can be exhausted very quickly if clients reconnect frequently

see also https://forum.netgate.com/topic/161324/openvpn-is-not-working-if-client-is-reconnected-immediately