Using Outlook for iOS for personal email and calendar management
Sorry to hear you're having trouble.
In addition to the information already provided I would like to recommend that you have your father contact support via https://support.microsoft.com and click on Contact Us. Note that support would only be able to help the account holder and no one else so it has to be your father.
The reason I suggest this is because getting help for your father could possibly require personal information that only support would need.