Service prin - reading Active directory

I have hit a snag.  I am writing a PowerShell script in an Azure App that will respond to events inside of my Key Vault subscription.  For example a secret has expired or is about to.  I can pull the vault down (get-AZKeyVault), examine the secrets but I need to get the Display Name of the access policy list so I know who to send emails too.  When I use my Microsoft creds this works fine.  When I use a SP I do not get this data. I get the object Id but not the display name.  What should I do to fix that?