Act/Act HA and MGMT interface FG300E v5.6.4

  Hi all, I have the same issue on FG300E v5.6.4:

https://forum.fortinet.com/tm.aspx?m=153225

"mgmt1 doesn't show up under act/act HA setup when I enable Management  Interface Reservation. I am connected to that interface to config it, but not a selectable interface....all other interface show up."

Port16 not selectable, is the "Management Interface Reservation"

(see image attached)

But i not have any static route on root VDOM.

Any suggestion is wellcome . Thanks!