When in suspended state, the device no longer participates in high-availability election process. In suspended state, communications still happen between the firewalls in the HA pair and this is not the same as disabling HA.
Resolution
Before making the node functional, consider the following recommendations :
Investigate and the fix the issue of the interface and/or path monitoring flaps.
If the node is made functional in an unstable environment, it will likely move into a suspended state again.
Remove the preempt option from the nodes until the monitoring status is stable.
This will help the healthy node retain the Active state, while the node encountering flaps will remain in the non-functional/passive state for investigation.
To make the suspended device participate in High Availability again, use the below methods.
CLI:
> request high-availability state functional
Web-GUI:
Navigate to Device -> High Availability -> Operational Commands ->Make local device functional