iOS 12 - NSFaceIDUsageDescription all of a sudden not working - ios

Question

I was using NSFaceIDUsageDescription in my app and it was working. I deleted my app from my device and and re-uploaded (plugging my device into my mac and running from xcode) it and now I don't get the alert that my app would like to use FaceID, how come the alert is not appearing anymore? This is preventing me from using FaceID in my app.
class TouchIDAuth {
let context = LAContext()
func canEvaluatePolicy() -> Bool {
return context.canEvaluatePolicy(.deviceOwnerAuthenticationWithBiometrics, error: nil)
}
func authenticateUser(completion: #escaping (NSNumber?) -> Void) {
guard canEvaluatePolicy() else {
completion(0)
return
}
context.evaluatePolicy(.deviceOwnerAuthenticationWithBiometrics, localizedReason: "Logging in with Touch ID") { (success, evaluateError) in
if success {
DispatchQueue.main.async {
completion(nil)
}
} else {
let response: NSNumber
switch evaluateError?._code {
case Int(kLAErrorAuthenticationFailed):
response = 2
case Int(kLAErrorUserCancel):
response = 3
case Int(kLAErrorUserFallback):
response = 4
default:
response = 1
}
completion(response)
}
}
}
}
And when I do this:
let touchMe = TouchIDAuth()
print(touchMe.canEvaluatePolicy())
The print returns false.
Is this an issue with my device? Or with NSFaceIDUsageDescription?

Answer 1

When your device exceeds the limit of incorrect attempts it usually returns false.
Try locking your device, then unlocking with face/touch ID and it starts working again in your app.
It should also return an error code why it is failling for evaluateError
Hope this was your case and solves the issue.