Hello Jesús,
I suggest then that you install and run tcpdump on the Access Server and monitor ICMP PING messages while you ping from the VPN client to the target IP. You will then be able to see the incoming pings and seeing them going out onto your network. With that confirmation you'll know the issue is not in the Access Server. You'll then have to look at firewall settings on the device that is receiving the pings, and try to address why it is not responding to them. You may also use WireShark or tcpdump on that target system too to confirm that pings are coming in. You're going to have to do network diagnostics to find the exact breaking point. But my guess would be it's just a Windows machine with its standard firewall rule blocking pings, or some security software like an antivirus+firewall thing that blocks it.
You may look at this document for further guidance:
https://openvpn.net/vpn-server-resources/troubleshooting-reaching-systems-over-the-vpn-tunnel/
Good luck,
Johan