Active-Active HA Problem (Slave device is unreachable)

Dear guys,

We have two FortiGate 300E in an active-active cluster. HA port is up, configuration sync is OK and everything looks fine.

But the slave device is unreachable. We cannot ping any interface on slave device when directly connecting the slave device to laptop. Ping reply is "destination host is unreachable".

Then I enabled load-balance-all through command line, but same result.

Do you have any suggestion?

Thanks