HA missing from FortiOS 5.6?

Hello all, I'm new to fortinet world, its look like an amazing device i have 2 units 100E with 5.4 firmware, i manage to setup HA active-active or active-passive, no problem. once i upgrade the machines to 5.6 the HA is gone and the option to set it up disappear . any other changes  in 5.6 that no HA option ? if there is how do i set it up ? thanks