Microsoft Outlook PST is just like any other database. It contains indexes to locate its file objects for better performance and speed. The objects can be e-mails, notes, calendar, contacts, tasks, appointments, and many others. But when these indexes get corrupted (generally because of unexpected power outage or using an indexing application), it can lead to complete inaccessibility of file and prevent MS Outlook from starting.
Its more of PST corruption thing, which can be resolved by using some other third party PST recovery tools. As I can see you have already tried using ScanPST which did not help much.
If you are able to open that PST in Outlook client, then I would rather suggest to create a new PST and import all data from affected PST and then try importing new one into EV archive.