iPhone Touch ID Not Working

Introduction

Apple introduced Touch ID with the iPhone 5S, enabling better security and more convenience when unlocking your phone. But with it comes the extra complications of potential failure. Even though Apple has made this repair more difficult to perform with software locks, you're not out of luck. Have a look at the solutions below to get yourself sorted.

First Steps

Before undertaking any of the more time consuming solutions below, these are a few fundamentals to get you started.

Restart your phone. This may clear any software hiccups.
Be sure you're using a gentle touch. To get Touch ID to activate you only need to rest your finger on the sensor, not press the button.
Give the home button an external cleaning. Wipe with a damp microfiber cloth, or gently buff out any oils with a dry cloth. Lingering debris can interfere with the sensor's ability to see your fingerprint.
Remove your case or screen protector which may be obstructing the sensor’s ability to get a clean reading of your fingerprint.
Enter your passcode. The phone will default to passcode entry if you you have recently restarted or left the device locked for more than 48 hours. Touch ID will be unavailable until you do so.
Verify your phone and apps are up to date.

Causes

Software Corruption or Conflict

iPhones, like all computerized devices, can be subject to software defects or bugs. The phone may have encountered an error, a third party app is wreaking havoc, or the OS itself may have become damaged.

Delete your fingerprints and add them again to be sure that errors in your fingerprint data are not present.
If you’re encountering the issue only in a specific app, see if that app has any updates. App updates can be found by navigating to the App Store and clicking the account button in the top right corner.
iOS itself may also need an update. In the Settings menu, under General, there is a selection for Software updates. You may want to process a backup before initializing the update to be sure your data is safe.
Perform a factory reset. In the case of potentially faulty software, it is recommended to try the reset via a PC with iTunes or a Mac. This installs a fresh copy from Apple rather than reinstalling from your device.
- When testing after the reset, it is best to set up as a new device. Resist the urge to restore your backup until you have confirmed the hardware is functional on a bare OS.

Physical Damage to the Button

Just like anything else, physical breakage or liquid contact can cause the home button to stop functioning. This is more prevalent on the touch sensitive style buttons present in the iPhone 7 or newer, but can occur regardless of model.

Check for signs of cracks in the button itself. Similar to a touch screen, capacitive-type buttons can lose functionality if the glass is damaged. Change your viewing angle to spot small hairline cracks.
Since the home button is not a continuous part of the display, it is prone to liquid entry. Damage of this type may be harder to see, but you may note rust or signs of corrosion with close inspection of the button’s back side.
If this is the case, and Touch ID is important to you, having your screen replaced by Apple is presently the only solution. The Touch ID sensor cannot be replaced independent of the display and Apple's pairing software is necessary to allow Touch ID to function.

Torn Cables

Many of the issues surrounding home button functionality are a result of repair attempts. The home button assembly itself uses tiny ribbon cables to transmit its electrical signals. As such, they are easier to damage inadvertently.

The cable which carries the Touch ID signal from the display to the logic board is commonly torn. It is the outermost cable connected to the display and susceptible to damage if tools are used improperly. Use a functional display to test if this is the issue. If this restores function, replacing the display is recommended.
Check for tears in the flex cables attached to the home button itself. They appear most often in corners and can be difficult to spot with the naked eye. If your cable is torn, and Touch ID is a necessity to you, seek repair from Apple. Repairing the home button cable to restore Touch ID is feasible, but requires running tiny jumper wires. Even many seasoned microsolderers avoid these repairs.

Not Native Home Button

The logic board and home button from any iPhone with Touch ID are paired together by Apple during the assembly process. If your screen was replaced by an independent repair shop, or you replaced it yourself, this button needs to be moved from the original screen to the new one to retain fingerprint reading capabilities.

If you still have your original home button, use the corresponding Guide to transplant it to the new display.
If you do not, getting a screen replacement from Apple is presently your only option. They alone have the ability to pair a new home button to a logic board. If you have an iPhone SE 2022, you have the option to repair it yourself, but be aware of the caveats of Apple’s Self Repair Program.

Logic Board Malfunction

The logic board is the hub for the vast majority of an iPhone's functionality. Any number of the small components on the board may have failed or become damaged, and is a safe assumption of cause if nothing else on this page has worked.

Check for obvious signs of a board issue - burned or cracked components, liquid residue, corrosion or bend. If there are signs of liquid the iPhone Liquid Damage Guide might help.
Replacing the logic board is often the most practical solution for a DIYer whose board has failed. But due to Touch ID pairing, replacing the board will break fingerprint reading functionality in all cases and home button function as well in the iPhone 7 and newer.
Contrary to popular belief, the board itself can be repaired. However, it requires specialized tools and microsoldering know-how. This is not something most people can do themselves, but many independent repair shops can do it for you! Ask around to find a board level repair specialists near you.