After replacing a cracked smartphone display assembly, a technician confirms the new screen and touch interface work correctly. However, the phone now requires the user to enter a PIN at every unlock, and the settings menu reports that the fingerprint reader is unavailable. Which of the following repair steps was MOST likely skipped or done incorrectly?
Re-calibrating the ambient light and proximity sensors
Updating the phone's APN and carrier configuration
Replacing the SIM tray seal to restore proper pressure
Reconnecting or transferring the original fingerprint sensor cable to the logic board
Fingerprint unlock relies on a small biometric sensor that is usually built into the home button or power button flex cable. During a screen swap, the original sensor (or its flex-cable connector) must be transferred and firmly seated on the main logic board. If that cable is left disconnected, damaged, or replaced with a non-paired part, the operating system disables biometric authentication and forces PIN entry. Problems with an ambient-light sensor, SIM tray, or carrier settings do not affect the fingerprint module, so they would not cause the biometric feature to disappear.
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Why does the fingerprint reader stop working if the original sensor is not properly reconnected?
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What does a fingerprint sensor's flex cable do, and why is it crucial?
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How can a technician ensure a fingerprint sensor works after replacing a screen?