I have VPN gateway installed in proxy mode. The client is able to reach all internal network resources though SMB, HTTP, etc. but it can’t ping them as well as any internet hosts. At the same time it’s able to ping VPN gw itself (10.9.0.1).
I.e. 192.168.0.х hosts are reachable though browser and Windows explorer while they are not pingable.
This is the known disadvantage of proxy mode, which is limited to TCP and UDP protocols only. I will consider adding some sort of ICMP proxy in the future, but meanwhile if you need ICMP then you can switch gateway to the NAT mode.