Check the status bar at the bottom of the screen to see if another process is Outlook repair support team running. If so, wait a short time (usually two or three minutes) to see if Outlook starts working again. Customers with only a 3rd party email address set up as the username of their Microsoft Account will be asked to add a 1st party Microsoft alias to their account before accessing Outlook.com. You might need to set Windows Update to automatically download and install recommended updates.
These applications and services can interfere with Outlook. A Selective Startup or "clean boot" process can help you identify problems that are caused by application conflicts. Corrupted PST or OST data files can prevent Outlook from loading. Microsoft’s ScanPST tool can repair minor corruption