Hi @Kapilp534,
Is that a SmartCenter Management or a Multi Domain?
Also, have you upgraded through CPUSE or was it an advanced upgrade using export/import?
In case FWM is down after upgrade, it might indicate that the upgrade failed. In case of CPUSE upgrade usually the machine is reverted automatically to R77.30 but in case you performed an advanced upgrade and for some reason you missed the error message that was presented in your console, we have a protection mechanism that prevents FWM from loading in case the upgrade failed.
Another option is that the upgrade process succeeded, but now there's a problem with FWM post upgrade.
I recommend opening a ticket to TAC so they could guide you and check what is the reason for the failure.
Eran