Another program is trying to access mu outlook data

That sounds like classic Outlook’s Object Model Guard, which checks certain operations made through OLE/COM automation. Running your app as administrator will not bypass it. Your code is accessing Outlook’s object model, rather than reading the PST directly.

Since the warning started after years of normal operation, check this first:

1. In Outlook, open File > Options > Trust Center > Trust Center Settings > Programmatic Access.
2. Check the Antivirus status shown there. If it says inactive, invalid or out of date, check Windows Security > Virus & threat protection > Manage providers and make sure your antivirus is active and updated. Restart Outlook afterward.
3. If the antivirus status is valid, check whether Outlook is configured to always warn. On a managed computer, your administrator may control this setting.

Outlook does not offer a simple “always trust this executable” list for external automation apps. The Never warn option, where available, removes protection broadly rather than just allowing your app, so it is not a good per-app solution.

For a code fix, identify the exact property or method that triggers the prompt. Basic appointment fields such as Subject, Start and End are generally not what triggers address-access warnings; reading recipient addresses or other protected properties can. If your display only needs dates and titles, removing unnecessary protected-property access may eliminate the prompt.

If protected access is essential, Outlook Redemption is an established third-party option for accessing Outlook data through Extended MAPI. Check its licensing and deployment requirements. Elevating your existing OLE code is not the fix.