NativeFirebaseError: [auth/unknown] an internal error has occurred. [ internal error encountered.]

I integrated the React Native firebase phone number authentication before 2 days. It was sending the OTP messages to all the numbers using this code

async function signInWithPhoneNumber(phoneNumber) {
const confirmation = await auth().signInWithPhoneNumber(phoneNumber);
setConfirm(confirmation);
}

Now after 2 days, it is giving an error

NativeFirebaseError: [auth/unknown] an internal error has occurred. [ internal error encountered.]

When try to send send OTP.

My integration is fully according to the firebase documentation. Sometimes it sends an OTP, but most of time, it gives that error for Android.