I am currently able to view the content of the Sustainability private beta although I am not logged in.
I was invited and do have an account, but I assume this is still a bug.
I logged in this morning. But currently it appears as though I am logged out. When I came onto the MSO site it shows 2 notifications. It appears as though I am not logged in at all o the Sustainability site.
I am on an iPhone.
I have taken a screenshot withy iPhone and can share latter if requested.