I found the problem. It's the route/gateway of VPN didn't work.
As pfsense cannot accessing the server in the other side of the VPN, I need to create a gateway with the same IP as the LAN interface on LAN interface. And than set a route to the subnet of other side of the VPN via this gateway.
In the new snapshots, the gateway/routing is missing. That's why I cannot resolve the domain which is queried by the server in the other side of the VPN.