I would start analyzing this by checking what logs are showing. Do you see logs for traffic from VPN client virtual adapter IP address?
For site-to-site VPN, does logs show that traffic is allowed through correct VPN? If yes, do you see outgoing ESP packets sent to remote GW IP address using (correct) outbound SPI? If you see packets sent out with outbound SPI, do you see those packets reaching peer GW and do you see logs on peer GW for traffic that should be coming through VPN tunnel?