ISG accounting fails on C7200

I'm totally stuck.
We are using Cisco 7200 NPE-G2 with 12.2(33)SRE2 IOS with ISG features.
On ethernet connected clients we discover a problem, that no accounting happens.
Client's subinterface configuration is like this:

int g0/1.2001
enc do 2001
ip vrf forwarding InterNet
ip address <Internet address>
service-policy type control IPN-VPN
ip subscriber interface

policy-map type control IPN-VPN
class type control IPN-UNAUTH event timed-policy-expiry
10 service disconnect
!
class type control always event session-start
10 authorize aaa list IPN password 123 identifier nas-port
20 set-timer UNAUTH-TIMER 5
30 service-policy type service name Deny-IPN
40 service-policy type service name AllPermit-IPN
!
class type control always event session-restart
10 authorize aaa list IPN password 123 identifier nas-port
20 set-timer UNAUTH-TIMER 5
30 service-policy type service name Deny-IPN
40 service-policy type service name AllPermit-IPN
!
class type control always event quota-depleted
1 set-param drop-traffic FALSE


All ISG services refer to accounting list PPTP:
aaa accounting delay-start vrf InterNet
aaa accounting update periodic 5
aaa accounting network PPTP
action-type start-stop
group PPPoEN

Debugging "deb sss feature name accounting" shows:

Sep 9 16:35:36: SSS MGR [uid:241]: Failed to initialize aaa accounting event
Sep 9 16:35:36: SSS MGR [uid:2296]: Failed to send aaa event

Tcpdump on radius server shows nothing.

What's wrong with configuration? Thanks for any reply