The session is showing that the udp 500 traffic is properly permitted and NAT is working here.
Session ID: 316147, Policy name: VPN_PPTP/40, Timeout: 36, Valid In: 82.132.227.76/627 --> 200.200.200.202/500;udp, If: ge-0/0/5.0, Pkts: 2, Bytes: 728 Out: 10.10.10.10/500 --> 82.132.227.76/627;udp, If: vlan.40, Pkts: 2, Bytes: 524
What do the server logs show at this point? Do they see the connection attempt?
With this configuration active I would do a packet capture on the L2tp server and see what the conversation looks like. Especially the reponse packets from the server. The flow shows that both the inbound and outbound packets are present and permitted. So this is likely an application level issue.