I think we both have the same issue. I had exactly the same problem, and I tried all sorts of routes on the client and target to get this working. Then i did what I should have done from the start and Wiresharked it.
The results show that my pings are actually getting out onto the private subnet, the problem is the boxes they're hitting have no idea where the packets have come from. So instead of the responses going back to the IP of the VPN client, they're going back to the VPN assigned DHCP address. In the private subnet this is meaningless, and the responses just gets lost.
To prove this I added a route to one of the boxes I was pinging so that 172.27.232.0 got routed back to my OpenVPN client. It worked!
Basically I have no idea how the Turtle works, but then I don't understand how many things work! From my point of view the router in the private subnet would need to know where to send the VPN traffic for this to work.
https://docs.openvpn.net/how-to-tutorialsguides/virtual-platforms/site-to-site-layer-3-routin-using-openvpn-access-server/
The only way I can see this working is by SSH'ing onto the target and then working from there. At the moment mine is saying Connection Refused for whatever reason. Another problem to work out!
