Using New Outlook on Windows for professional communication and productivity
I also had the issue of the settings window stuck on 'loading...' - I believe the cause, for me at least was having an office365 email account setup that I removed from the server. (i.e the mail account no longer existed in office365).
The only way to resolve was to remove the contents of: \AppData\Local\Microsoft\Olk and setup the new Outlook again from scratch.
Some one at MS needs to check why the settings window gets stuck when there is an issue with one of the accounts.