As an Office 365 user, you want to install an app from the Office Store. When you're prompted, you enter your user name and password. However, you cannot sign in. Instead, you receive a message that resembles the following:
You’re currently signed in with an organizational account. To continue with this purchase you need to sign in with a Microsoft account. You will be asked to do this on the next page.
This issue occurs if you enter the user name and password of your Office 365 account instead of the user name and password of your Microsoft account.
To install apps from the Office Store, enter the user name and password of your Microsoft account.