I used VPN to connect site-to-site private networks from A to B. It worked fine. Then I used NAT for (1) hiding private networks and (2) LAN of 2 sites could access the Internet. The problem is that they cannot access each other.
The interruption occurs at router Internet. Looks like it doesn't know which is the next hop to send packets because I used NAT to hide private addresses. So the VPN doesn't work either. How can I fix this?