Follow up since I saw some activity here - after it repeatedly not working, not knowing exactly how Legend works I just did some things I hoped would update/reset any email configuration as much as possible. After logging out of O365, switching over to Gmail (which worked), then back to 0365, logging in and out of O365 a couple of times, I left the email pane loading and the Outlook emails came through and the issue was fixed some time later, maybe after around 5-10min?
That said, with the latest update, double-clicking and opening single emails now appears to be broken, it opens outlook, but the single email area is just blank/white. 
