Outlook keeps asking for a password on setup. You have to remove the credential to resolve the issue.
Many a time it happens that a setup of an email address in Outlook stalled out because you couldn't get past a popup that kept asking for a password. It doesn't matter how many times you enter the password correctly, the profile will not setup. This is usually a result of an old set of credentials for that profile (namely the email address related to that profile) that is still listed in the 'Credential Manager' of your computer and needs to be removed before you can set up the mailbox. It remembers those old credentials in the Credential Manager and that supercedes whatever you submit into the password field.
The Credential Manager serves, generally speaking, to help make your life easier and remember usernames and passwords so you can log straight into things. Every once in a while, however, when you have to replace or update a credential from somewhere peripheral to the Credential Manager (the Mail app, a regular browser at times), it doesn't stick and the stored stuff Stay even when you update elsewhere. This happens a lot with email, particularly when switching email types like when upgrading from POP/IMAP or Hosted Exchange to Office 365 Email.
You remove the mail profile from the Mail app, but it still exists in the Credential Manager, so you want to go in and remove it so that next time you add it, it is like it is brand spankin' new. This is pretty deep level stuff as far as the computer is concerned: this is just a list of stored logins(credentials) that your computer remembers, taking this out here is taking it right out of the system for keeps.
Let's Manage Some Credentials!
Navigate to your Credential Manager:
Identify the credential to remove.
Get out of the Credential Manager and begin adding the mail profile again. Should work like a charm