Hello, Here are some ways to troubleshoot: '''Clear Cookies and Cache: '''Click the padlock icon in the address bar, select "Clear cookies and site data," then reload the page. '''Use Private Mode:''' Open a new private window (Ctrl+Shift+P) and attempt to sign in to https://outlook.office.com/mail to check if extensions are causing the issue. '''Disable Extensions/Tracking Protection:''' Turn off ad-blockers or privacy extensions (e.g., UBlock Origin, Privacy Badger) and check that Firefox's Enhanced Tracking Protection is not blocking the site. '''Troubleshoot Mode:''' Start Firefox in Troubleshooting Mode (formerly Safe Mode) to determine if an add-on is responsible. '''Verify Account Status:''' If the error persists, the account might be blocked due to unusual activity; check at Microsoft Support. If you are using bookmarks, make sure to use the direct URL rather than an outdated one.