OpenVPN plugin: openvpn service won't start

[piereligio]

I've really tried many things to fix this including installing on different versions of FreeBSD, but I can't make openvpn service start on TrueNAS-12.0-U5.1.
Basically right after doing the first setup of the jail, the service will crash right away.
These are the last lines before the crash (from /var/log/messages) :
OpenVPN openvpn[4056]: /sbin/ifconfig tun2 10.8.0.1 10.8.0.2 mtu 1500 netmask 255.255.255.255 up
OpenVPN openvpn[4056]: FreeBSD ifconfig failed: external program exited with error status: 1
OpenVPN openvpn[4056]: Exiting due to fatal error

What can I do? Thanks in advance

[RossComputerGuy]

Try specifying a different tun, check if it is listed in /dev and in ifconfig.