Here's the query that is failing: https://graph.microsoft.com/beta/me/files (It's also present in the Microsoft website here: https://msdn.microsoft.com/en-us/office/office365/howto/office-365-unified-api-overview?f=255&MSPPError=-2147217396)
The error message I am getting is:
Resource not found for the segment 'files'.
Thanks