Fortigate 3600C HA issue and it's halted

[Bhuvan]

We are using 2No's FortiGate 3600c firewall in HA  (Active-Active) mode. Due to maintenance activity we have shutdown slave firewall. after booted slave firewall when we are connecting HA cable between slave and master firewalls. slave firewall is going to sleep mode and it's halted.

Kindly provide any suggestion on this issue.

[AEK]

As it happens what do you see in HA logs (Log & Report > Events > HA events)?

Please share the output of the following commands:

diag sys ha history read

Type the following commands then power on the slave node to collect HA formation info.

diagnose debug enable
diagnose debug console timestamp enable
diagnose debug application hatalk -1
diagnose debug application hasync -1

While powering on the slave node, connect to its console port and check if there is any relevant output, like a hardware failure or HA related errors.