When going onto account usage and you attempt to download your M2M usage for any of the three options. The downloaded file is corrupted and not a valid csv file. For example, it cannot be opened by MS Excel.
‘Account Usage’ > ‘Machine to Machine Auth’ > ’ Authentication Calls by Application - Daily’ > ‘Download CSV’
I just went to my account usage section and downloaded .csv report regarding m2m usage and opened it using following version of Excel and everything works fine.