Firebase Authentication with phoneNumber failed with Internal error - swift

Question

I want to use Firebase SMS Authentication with phone number.
I have already enabled push notification in my app setting and registered Firebase Apns authentication key as google document says.
However, after I sent phone number with country code, Xcode says,
Failed to receive remote notification to verify app identity within 5
second(s)
Error says as below:
error: Error Domain=FIRAuthErrorDomain Code=17999 "An internal error has occurred, print and inspect the error details for more information." UserInfo={error_name=ERROR_INTERNAL_ERROR, NSLocalizedDescription=An internal error has occurred, print and inspect the error details for more information., NSUnderlyingError=0x28329c8a0 {Error Domain=FIRAuthInternalErrorDomain Code=3 "(null)" UserInfo={FIRAuthErrorUserInfoDeserializedResponseKey={
code = 500;
errors = (
{
domain = global;
message = "Internal error encountered.";
reason = backendError;
}
);
message = "Internal error encountered.";
status = INTERNAL;
}}}}
My code:
PhoneAuthProvider.provider().verifyPhoneNumber(phoneNumber, uiDelegate: nil) { verificationId, error in
if let error = error {
print("error: \(error)")
return
}
print("verificationId: \(verificationId!)")
UserDefaults.standard.set(verificationId, forKey: "authVerificationID")
self.goToSecondVC()
}
Any idea??