Why isn't Outlook notifying me of my emails?

[AC Question]

I have recently upgraded to a Huawei P9 and used the Oitlook app to have all my emails in one place. However, although the phone and app settings have been set to allow notifications, make a sound and allow priority notifications I'm still not getting them. I have to physically open the app and then I see my new emails. Does this sound like an app problem or is it the phone? Thanks