OpenVPN server with two Radius auth servers in failover

[mrachilli]

Hello,
I am trying to set-up an OpenVPN server with two Radius authentication servers in failover. I have checked the functionality of the two servers individually and then proceeded to add them to the configuration options by selecting both with Ctrl+click.
The servers are added alphabetically, I cannot choose the order in which they are added. If I stop the Radius service on the first server or take down the machine it runs on the authentication process does not succeed by using the second server.

I have checked the PFsense logs and strangely this message appears:
Feb 5 11:24:41 openvpn 32104 /openvpn.auth-user.php: Error during RADIUS authentication : Operation timed out
Feb 5 11:24:41 openvpn 32104 user 'martin.achilli' authenticated

Unfortunately on the OpwnVPN client side the authentication fails and after a timeout I am prompted for credentials again. PFsense CE version 2.72, NPS/Radius on Windows 2016/2019

Thank you,
Martin