Content The Additional Details provides more details and often tells you how to resolve the issue. For iPhone users, reinstalling Outlook or updating to the latest iOS often resolves stuck sign-in loops instantly. Many users have both personal Microsoft accounts (e.g., Outlook.com) and work/school Office 365 accounts. If both are signed in simultaneously, the system can confuse the authentication path. Log out of all accounts and sign in with only one — preferably the one with your Office...