400 bad request Invalid session

There is a router accesses the Internet through NAT, and then connect to the ACS,
ACS responded “400 bad request”, as the log shows

where is the problem? What could I do to fix this?
Please help me !

Invalid session would mean that the cooike value is not correct. If you look closely when server make GPV it doesn’t use any cookie, however when your device replys in header you can see cookie. Either there is some proxy or relay in your path which sets the cookie.

do you know how to solve this cookie problem?

Yes. The problem was with load balancer (haproxy) I had to use sticky table and now it runs great.