The appliance has crashed and won't boot.
I assume that you already tried to fix the issue, but without success.
Can use Veeam to recover the appliance.
If this is "static" environment - i.e. not many changes since the last backup - a restore might be the easiest way to resolve the issue.
Can it be reinstalled?
Basically yes, but it depends on the features that are in use (e.g. distributed virtual switches, etc.) what needs to be taken care of after reinstalling it.