Can't Sign into Microsoft 365 on Mac – Error [2604]

Issue

Microsoft 365 sign-in fails on macOS with this error: No Network Connection. Please check your network settings and try again. [2604]

Environment

• macOS
• Microsoft 365

Resolution

1. Remove Microsoft Apps

   • Open Finder > Applications
   • Delete all Microsoft apps

2. Clear Keychain Entries

   • Open Keychain Access
   • Search “Microsoft”
   • Delete all items (certificates may remain)

3. Update macOS

   • Go to System Settings > General > Software Update
   • Install all updates

4. Reinstall Office

   • Detailed instructions available here

5. Sign In

   • Open any Office app
   • Sign in with your Duquesne Microsoft account