BIG IP ASM : can't create a new policy. The action is aborted due to CSRF attack

I am in version V11.6.3 when I try to create anew security policy by : Security/appplication security/security policies / + . The action is aborted and get the message : "This request was unauthorized. The system detected a CSRF attack, and so the action was not implemented. Click Here to continue working on the system." Thanks for your help in advance