SharePoint Audit log reports on opened/viewed documents

I am trying to create an audit log report that should show who and when viewed documents in specific libraries in my site.

I have activated Reporting and enabled audit settings.

I have two problems 1) there seems to be something wrong with the audit report, it says 'Couldn't open workbook. It is possibly corrupt or using a file format that's not supported'

I can open the file in Excel (but it still has the error message).

However, I can't see 'viewed' in the Event columns, only Update. How do I set it up to show 'viewed' documents?