iRule for ASM response page and error when use HTTP::respond

You can try the following (untested):

when ASM_REQUEST_DONE {
    set x [ASM::violation_data]
    for {set i 0} { $i < 7 } {incr i} {
        switch $i {
        0         { log local0. "violation=[lindex $x $i]" }
        1         { log local0. "support_id=[lindex $x $i]" }
        2         { log local0. "web_application=[lindex $x $i]" }
        3         { log local0. "severity=[lindex $x $i]" }
        4         { log local0. "source_ip=[lindex $x $i]" }
        5         { log local0. "attack_type=[lindex $x $i]" }
        6         { log local0. "request_status=[lindex $x $i]" }
        }
    }

    if {([lindex $x 6] == "blocked")} {
        In this case we only use 2 parameter: support id and source ip
        set supportid [lindex $x 1]
        set sourceip [lindex $x 4]
        set blocked "blocked"
        ASM::unblock
    }
}

when HTTP_REQUEST_SEND {
    if { [info exists blocked] } {
        HTTP::respond 200 content "Test block pagePage is currently unavailable.
support id:$supportid
source ip:$sourceip" "Content-Type" "text/html"
        TCP::close
    }
}

.