Make the XG access its own ipsec tunnel

Hello,

I have some XGs in branch offices connected over IPsec site-to-site tunnel, I want to make the remote XGs to access my Head Office LAN, my objective here is to make the remote XGs to be accessible from the Sophos Firewall Manager, when I try to ping the SFM IP from one of the remote XG I can't reach it.

Thanks