Is Firebase not supporting Phone Authentication on Spark Plan? (LOG [Error: [auth/internal-error] An internal error has occurred, please try again.])

I am developing a mobile application based on React Native framework. Earlier, the Phone Authentication is working properly. But now it’s showing me error ([Error: [auth/internal-error] An internal error has occurred, please try again.]). I have tried many changes in firebase configurations and updated my code as well but still showing same issue. I’ll be very thankful who ever sorts this out.

Authentication Script:

  async function signInWithPhoneNumber() {
    const phoneNumber = `${countryCode}${contact}`;
    if (!contact.trim() || !password.trim() || !confirmPassword.trim() || !name.trim()) {
      Alert.alert('Register Failed', 'Please Enter all required fields.');
      return;
    }

    if (contact.trim().length < 10) {
      Alert.alert('Invalid phone number', 'Please enter a valid phone number');
      return;
    }

    if (password !== confirmPassword) {
      Alert.alert('Password Mismatch', 'Passwords do not match. Please try again.');
      return;
    }

    const userExists = await checkUserExists(phoneNumber);
    if (userExists) {
      Alert.alert('Registration Error', 'This phone number is already registered.');
      return;
    } 

    try {
      const confirmation = await auth().signInWithPhoneNumber(phoneNumber);
      setConfirm(confirmation);
    } catch (error) {
      Alert.alert('Failed to send OTP', 'There was a problem sending the verification code.');
      console.log(error);
    }
  }

Output: LOG  [Error: [auth/internal-error] An internal error has occurred, please try again.]