If you encounter a "Firmware Loading" error, a restart is often required to trigger the Gobi loader to push the firmware to the card upon boot.
The key challenge is that the un2420 appears to the operating system as a composite USB device. Upon insertion, it enumerates as multiple virtual COM ports (for GPS and diagnostics) and one modem port. Windows 10 lacks the legacy Qualcomm HS-USB Modem class drivers. hp un2420 mobile broadband module driver windows 10
Official Windows 10 support for the HP un2420 Mobile Broadband Module If you encounter a "Firmware Loading" error, a
HP stopped supporting this module in 2013. Windows 10 was released in 2015. Neither HP nor Qualcomm created a signed driver package specifically for Windows 10. Thus, any solution requires a workaround. Windows 10 lacks the legacy Qualcomm HS-USB Modem
However, with the advent of Windows 10, thousands of users have been met with a frustrating reality: the device shows up in Device Manager with a yellow exclamation mark, labeled as an "Unknown Device" or "HP un2420 Mobile Broadband Module" with Code 28 (driver not installed). Microsoft did not provide native drivers for this legacy Qualcomm Gobi hardware.
If you have succeeded, consider writing a forum post on HP Support or Reddit’s r/HPLaptops to share which driver package worked for your specific Windows 10 build. The community relies on collective memory to keep legacy hardware functional.