We have a corporate Office365 account. I have downloaded Excel to a company iPad and am trying to open a (basic, with no macros or protected cells of any kind, nor anything else on the "mobile Excel can't edit this" list) file containing some basic hardware inventory. The file, opened from OneDrive, opens in "read only" mode despite my repeatedly tapping the "Sign in" link and supplying my company e-mail address and password. This e-mail address, when used at login.microsoftonline.com, successfully brings me to our O365 account and I am able to edit the file in Excel Online.
Why is Excel for iOS failing to open the file in edit mode?