nmap HS through openvpn

[Bizbi]

hi
I have a behavior that I do not explain:

Context: personal environment, I have network knowledge

Need: I am trying to use the nmap tool from site A to a machine at site B via an openvpn tunnel without success. It works internally on site B.

Plan :
LAN_A ---- [PFSENSE_A] === TUN OPENVPN === [PFSENSE_B] --- LAN_B

WAN (modem / router / box): a public ip by pfsense.

NAT rules: automatic outbound

Firewall rules: for the purposes of the test: any / any

Added packages: frr / openvpn-client-export

Other functions assigned to pfSense: routes are propagated through the vpn in BGP (frr)

Question: nmap does not see the machines up through the vpn, the result is positive locally.

Imagined avenues: bad VPN or firewall conf?

Logs and tests: the firewall rules are any / any and the vpn conf works for everything else (ping, ssh, nas)