OpnSense OpenVPN OpenWRT S2S

Hello Everyone,

I'm banging my head over this for quite some time but I can't find a solution, so I am here to kindly ask for some help.

I have an OPNSense Firewall with a public IP on the WAN side, and LAN A
I configured an OpenVPN server instance tunnelling through

I installed OpenWRT 23.05.2 on an Archer C7 and everything went fine.
This router is behind a NAT so I have no public IP on the WAN side.
LAN B is

I configured the tun0 interface and the OpenVPN client, everything ok.
Tun0 is in the LAN zone of OpenWRT with masquerading enabled.

I can ping server's 50.0/24 from client's 31.0/24.
I can't ping client's 31.0/24 from server's 50.0/24.
I can ping (OpenWRT Tunnel) from 50.0/24.
I can ping (OPNSense Tunnel) from 31.0/24.

If I ping from 50.0/24 to 31.0/24 I can see traffic flow on the OVPN interface of OPNSense with TCPDUMP.
However I cannot see any traffic flowing to OpenWRT coming from OPNSense with tcpdump -i tun0.

Routes on OPNSense seems fine, I have done this kind of setups many, many times with both OPNSense as a server and client and everything worked like a charm.

Any advices on this?

Thank you all