If you have turned on Stolen Device Protection in iPhone Settings, this issue might occur on a lost device.
The best solution is to off lost mode on iCloud or another phone.
If you recently purchased the phone, returning it might be your only choice because it might have been stolen.
Fix 1: Turn Off Lost Mode in iCloud
You have to switch off your iPhone’s stolen device protection if you enabled it. If not, your phone can be considered a stolen item. Sadly, the only way to disable it is to turn off Lost Mode in iCloud, which requires Face ID.
Step 1: Click the Find My icon after logging into iCloud.
Step 2: Click your device, then select Lost Mode from the windows that appear.
Step 3: Press the button to exit lost mode.
Fix 2: Return the Phone to the Seller
If you just bought the phone, it was most likely a stolen or lost phone. Your best option is to return it to the seller and most likely receive a replacement or a refund if this is the case. In this scenario, you are able to fix the Face ID issue.
Fix 3: Contact Your Carrier
The mobile network provider may have reported the phone stolen or missing in some areas. To ensure that the phone is in the right hands, it is best to get in touch with the carrier in such circumstances.
The method for verification will vary based on your carrier. In the end, your phone will be removed as missing, and Face ID should function once more.
Fix 4: Contact Apple Support
Finally, you have to get in touch with Apple support. You can reach them by phone at 1 (800) 275-2273, through their dedicated help line, or through the Apple help app.
To verify your identification and device ownership, they will inquire about basic information from you. In the end, they will offer solutions for resolving the issue.