To fix this, remove the Outlook client configuration files that were corrupted. If you've installed the most recent macOS update, Outlook for Mac might stop accepting your password, which used to work just fine. To fix this, see this article from Apple to create a new login keychain or update it with your new password. If your macOS user account password was recently reset, it might not match the password of your login keychain. Here are two possible solutions: Your macOS password was reset
You attempt to sign in to Outlook for Mac, and even though you've entered the correct password, Outlook doesn't accept it and continues to ask for your password. Outlook for Mac isn't accepting my password
