Cookie Persistence iRule not working

And the persistence config is :

ltm persistence cookie cookie {
    always-send disabled
    app-service none
    cookie-name none
    defaults-from none
    description none
    expiration 0
    hash-length 0
    hash-offset 0
    match-across-pools disabled
    match-across-services disabled
    match-across-virtuals disabled
    method insert
    mirror disabled
    override-connection-limit disabled
    partition Common
    timeout 180
}