Fixing Onenote’s “Sorry, another account from your organization is already signed in on this computer” on OS X

I spent this afternoon fixing this, so I thought I’d share what I found.

It seems that when trying to sign into OneNote on OS X using Office 365, one can run into trouble signing in, especially if you’ve used OneNote on the system before with another Office 365 account.

I’d originally tried to find the files that OneNote was using using lsof on the command line. While I still recommend this, truthfully I don’t think this is what fixed it. I’d start doing this with Office Uninstalled is that Office and OneNote are somewhat intertwined, and you’ll probably hork up your Office install by performing these steps and will need to reinstall it anyhow.

In any case, you should get a list of files that OneNote is hanging on to when in runs. With OneNote15 on OS X Yosemite I found the following:

'/Users/kris/Library/Group Containers/UBF8T346G9.Office'
'/Users/kris/Library/Saved Application State/'
'/Library/Logs/DiagnosticReports/Microsoft OneNote'

For the command line savvy, just do the following to find your OneNote files, on my system, using locate seemed to ignore many of the directories in question:

find / -iname onenote

This will find the directories above for your user. Uninstall OneNote. I installed mine from the app store, so that required me to go to launchpad, find onenote, hold down the mouse button till it jiggles and press the circle x that appeared.

Afterwards, delete the directories you discovered since the uninstall process won’t.

Next is the step that I think really fixed the issue.
* Open up the Keychain Access app.
* Select “Passwords” on the right under “Categories”
* Search for “Office”
* Delete everything you find in there, you’ll likely see a few items such as:
** Microsoft Office Identities Cache 2
** Microsoft Office Identities Settings 2
** A credential key with a GUID for a name. It’ll have a blue @ sign.

After that, install OneNote, and try to sign in. In my case, the error was no longer present, and I was able to sign in using my Office 365 account.