How do I show an outlook calendar in sharepoint 2013 online?

I have a shared outlook calendar in outlook 365, and I'm trying to show it on a calendar in SharePoint Online.

I've added it in the "Calendar Overlay Settings" screen, and saved it but when I view the Sharepoint calendar I see the error:

The HTTP request is unauthorized with client authentication scheme 'Ntlm'. The authentication header received from the server was 'Basic Realm=""'

My settings are Outlook Web Access URL: "http://ift.tt/18Mwss9" Exchange Web Service URL: "http://ift.tt/1hul7j1"

I've seen a few other post where people are getting a similar problem, but no solutions.

Does this work at all?