I upgraded may backup node and then did a failover to (persistent CARP switch) to upgrade the old master.
The OpenVPN client could not create a tunnel.
I switched back to the master with old master and the tunnel came up.
Does the OpenVPN configuration needs a change with 25.1.7, related to:
openvpn: add port-share as advanced feature
openvpn: add (push) block-ipv6 option