If you're stuck in a Microsoft 365 login loop, start by clearing your browser’s cache and cookies. Then, close all browser windows and reopen them. Go to portal.office.com and try signing in again. Ensure third-party cookies are enabled, as disabling them can trigger the login loop. If you're using saved credentials, try logging in via an incognito window to bypass cached sessions. For persistent issues, update your browser or try a different one. This helps resolve most microsoft365 portal login errors effectively. If problems persist, check your organization's conditional access policies or contact IT support for further assistance.