Update (07 Oct 2019) I discovered two configuration issues with the guidance in this post which I have now corrected.
The V1 EndPoints must be used rather than V2 Include https://graph.microsoft.com in the resource parameters Without these adjustments, K2 does not store a refresh token and it will expire daily.
For those organisations that use K2 Five and Office 365, the ability to use Microsoft Graph APIs in your forms and workflows is compelling. ...