Help - one side can't connect to another side on VPN IPSEC

hi there,

we've two network that connect by vpn IPsec.

I don't know where is the problem, either on the host (client pc) or setting on fortigate.

net_A connect to net_B by vpn ipsec.

net_A can ping to gateway net_B.

under net_B, remote desktop on PC has been activated, and user has been added.

but something error:

1. net_A can't connect / reach PC via remote desktop.

2. PC can't ping to net_A's gateway

3. one of PC under net_A (let say CPU), we use 3rd party software for client management, and can connect to PC under net_B (remote access, but not under RDP protocol, their protocol)

4. we have NAS under net_A. PC (under net_B) can't access to NAS, either we enter IP address nor client name on file explorer.

please help. thanks