I am getting a WAC token error when i try to access a drive item's workbook why?

Question

I am asking this here because i did a search and they give me this site as ms support for graph.

I am working by all items in a drive.
When i find a driveItem whose name contains .xls (a excel file) i must open the file and check for some data in the workbook to try to extract and tag the file.
My Code works for about 80% of the files but for some reason
When y try to open certain workbooks i get a

Error code: AccessDenied

Error message: Could not obtain a WAC access token.

GET https://graph.microsoft.com/v1.0/drives/b!jn6JlS9atkeM-KROA_T53TioJ9238OZLp2jmjTjLFfKXNoWAwIdzTpnXR6T0ZTsa/items/01THFQ36VJGBJMBQET4ZM234CASRKTDA4M/workbook

I tried using a AppClient with full admin rigths, and a user who is site owner and i am getting the same thing for some workbooks.

Can any one give me a hand with this?

Answer 1

I found out that my error was because of the excel version of the files.

The Workbook call only works on xlsx files, not on xls