Hi,
Please can you check / share output of the following ?
1> A topology diagram with components involved would be helpful in visualizing the scenario
2> From the RUT's CLI : ipsec status
2> Traceroute from the PC when on the client network towards the server and PLC and vice versa ?
3> Traceroute from the PC when on the server network and PLC and any other PC on the client network ?
4> A topology diagram with components involved would be helpful in visualizing the scenario
5> In the RUT's VPN config check if the "left firewall" and "right firewall" options are enabled
6> Is there any firewall rules, access controls on the either client or server side networks ?
Note : Please also check the following link for vpn configuration https://wiki.teltonika-networks.com/view/IPsec_configuration_examples
Thanks