For more information, follow this guide: short tutorial on how how to fix the conn.... Oct 14, 2021 ยท If only one or two machines are facing this issue, it is possible that custom port TCP 4433 is blocked by the client side ISP. Please try on a different ISP connection. Resolution for SonicOS 6.5. This release includes significant user interface changes and many new features that are different from the SonicOS 6.2 and earlier firmware.. "/>Error 638 broadband connection