Symptoms
Even if a subscriber identification module (SIM) card is correctly inserted in Microsoft Surface Pro LTE Advanced, Long-Term Evolution (LTE) connection can fail and result in "disconnected" status. In some cases, the Cellular option disappears from available network list and you cannot try this connection.
Cause
This issue may occur if a firmware update is made to an LTE modem with a history that has a specific SIM inserted. Because of the update, an inconsistency occurs in the Access Point Name (APN) information held in the LTE modem.
This is not an issue caused by mobile operators. We confirmed that the issue occurs depending on the inserted SIM and the APN information prepared in advance in the modem firmware for each carrier.
Firmware update is performed by automatic application by Windows Update or manual application of Surface Drivers and Firmware pack, but in both cases, it will lead to this issue.
In addition, you need an account that has administrator permissions to perform the update.
Resolution
If you want to prevent this issue, or if the issue has already occurred, you can recover by following these methods:
Install the following hotfix and restart the device.
Surface Pro LTE (5th Gen) Drivers and Firmware
If the "Surface Mobile Broadband" device firmware version is displayed as "190307-1128-REL-c7.1-00003", the firmware update is completed.
Note There is a chance you might have a different version of the Surface Updater installed on your computer. If you see error "A newer version of Surface Pro Update 19_015_07 (64 bit) is already installed", you need to open Add/remove programs and uninstall Surface update 19_035_01 (64 bit) or any other version of this tool.
Status
In cooperation with the Surface development department and the manufacturer of the LTE modem, we are offering new modem firmware that solved the problem. This hotfix will be released through Windows Update in the future.
