Really at a loss on this one. I've tried logging out and logging back in. Delete the Connections and re-add them. For whatever reason, no matter what I do, I can't get the Microsoft To-Do Connector to work with my Office 365 login. I have E5 licensing, so I don't think this is a licensing issue. I use other Connectors without problem, including ones that use an on-premises gateway and no firewall issues. So, some help would be appreciated.
I've confirmed that I do have permissions to use the app on the MS Admin Center. Just an on/off toggle I'm told by the IT admin and it's on :).
So what else could be causing this? I haven't run into this with any other connectors.