I assume the site on which the camera is has it's own internet connection?
The request TO the camera arrive correctly.
The problem is, that the answer goeas directly to the cameras default gateway and not back over the VPN tunnel.
What you can do is:
Disable automatically generated rules for the VPN. Assign the VPN interface. Enable advanced outbound NAT and create a NAT rule for the VPN interface.–> Set as destination the IP of the camera.
Like this , from the camera seen, the requests originate from the pfSense on the other side of the VPN tunnel
--> The answer will go back over the VPN.