I have two Microsoft Accounts: one for my personal use and another through my University. I sign into my computer (my personal computer) using my personal account, but am signed in to Microsoft Office (including OneDrive for Business) with my university account, as I am using their license. I have found recently that when I restart my computer sometimes (i.e. shut it down, leave it and later in the day turn it on) Microsoft Office will have signed in using my personal account (which does not have Office 365 linked to it). A tell-tale sign of this is that OneDrive for Business will ask me for credentials in a pop-up notification from the taskbar; when I click it nothing happens and OneDrive seems to resolve itself. When I open OneNote, for example, it has signed in with my personal account. I have yet to find any related factors in these incidents other than it tends to happen when I turn of my computer at one point in the day and then turn it on later.
Basically what I would like is for this to stop i.e. Office is signed in using my University account all of the time!
Another thing I feel I should mention, although is probably of no significance, is that I have added a profile picture to my University account, but that is not reflected in my Office products. This probably isn't relevant and I am not flagging this as an additional problem, just giving you all the information that may be of use.
I'm running Windows 8.1 Pro (signed in with my personal account) and Office 365 Pro Plus (signed in with my University Account), including OneDrive for Business which I use all the time.