aggregated ports 802.3ad going to cisco stacked switch

Hi i'm new to this,

Can someone please help me with this or tell me if this is possible.

Devices: 2x Fortigate 601e, 2x Stacked cisco catalyst 9500

edit "Outside"
set vdom "root"
set allowaccess ping https ssh http
set status up
set type aggregate
set alias "FGT_TO_CORE"
set device-identification enable
set snmp-index 27
next
edit "Ext_VLAN3"
set vdom "root"
set allowaccess ping https ssh
set forward-domain 30
set role lan
set snmp-index 28
set interface "Outside"
set vlanid 3
next
edit "Ext_VLAN999"
set vdom "root"
set allowaccess ping https ssh
set forward-domain 90
set role lan
set snmp-index 29
set interface "Outside"
set vlanid 999

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i'm having problem connecting aggregated ports on active active cluster going to stacked switches, ports on secondary firewall and cisco switch is suspended.

i really don't know what's wrong with my configuration, PS*** thanks for replying to this tread