What steps should I take if Error 1100 persists on my iPhone 6 Plus even after trying all common troubleshooting methods?

If Error 1100 persists after comprehensive troubleshooting (updating iTunes, trying different cables/ports, disabling security software, DFU mode), consider trying the restore process on a different, reliable computer. This helps rule out issues with your primary computer's operating system, drivers, or specific software conflicts. If the error continues on a second computer, it could indicate a more serious hardware issue with your iPhone 6 Plus, potentially requiring professional service.