Unity Google Sign in plugin with Firebase, App crashes with error configuration is null!? and Request not configured! Failing authenticate

GoogleSignIn.cs

namespace Google {
  using System;
  using System.Runtime.Serialization;
  using System.Threading.Tasks;
  using Google.Impl;
  using UnityEngine;
  
public class GoogleSignIn {

#if !UNITY_ANDROID && !UNITY_IOS
  static GoogleSignIn() {
    Debug.LogError("This platform is not supported");
  }
#endif

    private static GoogleSignIn theInstance = null;
    private static GoogleSignInConfiguration theConfiguration = null;
    private ISignInImpl impl;

        ///<summary> The configuration settings for Google Sign-in.</summary>
        ///<remarks> The configuration should be set before calling the sign-in
        /// methods.  Once the configuration is set it cannot be changed.
        ///</remarks>
        public static GoogleSignInConfiguration Configuration
        {
            set
            {
                // Can set the configuration until the singleton is created.
                if (theInstance == null || theConfiguration == value || theConfiguration == null)
                {
                    if (theInstance != null && theConfiguration == null)
                    {
                        //From sign out, Instance stays non-null but theConfiguration is null.
                        //Needs configuration refresh.
                        theInstance.impl.Configure(value);
                    }
                    theConfiguration = value;
                }
                else
                {
                    throw new SignInException(GoogleSignInStatusCode.DeveloperError,
                        "DefaultInstance already created. " +
                        " Cannot change configuration after creation.");
                }
            }

            get
            {
                return theConfiguration;
            }
        }

        /// <summary>
        /// Singleton instance of this class.
        /// </summary>
        /// <value>The instance.</value>
        public static GoogleSignIn DefaultInstance
        {
            get
            {
                Debug.Log("GSIn 1.0");
                if (theInstance == null)
                {
#if UNITY_ANDROID || UNITY_IOS
                    theInstance = new GoogleSignIn(new GoogleSignInImpl(Configuration));
#else
          theInstance = new GoogleSignIn(null);
          throw new SignInException(
              GoogleSignInStatusCode.DeveloperError,
              "This platform is not supported by GoogleSignIn");
#endif
                }
                Debug.Log("GSIn 1.1");
                return theInstance;
            }
        }

        internal GoogleSignIn(GoogleSignInImpl impl) {
      this.impl = impl;
    }

    public void EnableDebugLogging(bool flag) {
            impl.EnableDebugLogging(flag);
    }

        /// <summary>Starts the authentication process.</summary>
        /// <remarks>
        /// The authenication process is started and may display account picker
        /// popups and consent prompts based on the state of authentication and
        /// the requested elements.
        /// </remarks>
        public Task<GoogleSignInUser> SignIn()
        {
            Debug.Log("GSInUser 1.0");
            var tcs = new TaskCompletionSource<GoogleSignInUser>();
            SignInHelperObject.Instance.StartCoroutine(
              impl.SignIn().WaitForResult(tcs));
            Debug.Log("GSInUser 1.1");
            return tcs.Task;
        }

        /// <summary>Starts the silent authentication process.</summary>
        /// <remarks>
        /// The authenication process is started and will attempt to sign in without
        /// displaying any UI.  If this cannot be done, the developer should call
        /// SignIn().
        /// </remarks>
        public Task<GoogleSignInUser> SignInSilently() {
      var tcs = new TaskCompletionSource<GoogleSignInUser>();
      SignInHelperObject.Instance.StartCoroutine(
          impl.SignInSilently().WaitForResult(tcs));
      return tcs.Task;
    }

    /// <summary>
    /// Signs out the User.
    /// </summary>
    /// <remarks>Future sign-in attempts will require the user to select the
    /// account to use when signing in.
    /// </remarks>
    public void SignOut() {
      theConfiguration = null;
      impl.SignOut();
    }

    /// <summary>
    /// Disconnect this instance.
    /// </summary>
    /// <remarks>When the user is disconnected, it revokes all access that may
    /// have been granted to this application.  This includes any server side
    /// access tokens derived from server auth codes.  As a result, future
    /// sign-in attempts will require the user to re-consent to the requested
    /// scopes.
    /// </remarks>
    public void Disconnect() {
      impl.Disconnect();
    }

    /// <summary>
    /// Sign in exception.  This is a checked exception for handling specific
    /// errors during the sign-in process.
    /// </summary>
    [Serializable]
    public class SignInException : Exception {
      internal SignInException(GoogleSignInStatusCode status) {
        Status = status;
      }

      public SignInException(GoogleSignInStatusCode status, string message) :
          base(message) {
        Status = status;
      }

      public SignInException(GoogleSignInStatusCode status, string message,
          Exception innerException) : base(message, innerException) {
        Status = status;
      }

      protected SignInException(GoogleSignInStatusCode status,
                                SerializationInfo info,
                                StreamingContext context) :
          base(info, context) {
        Status = status;
      }

      public GoogleSignInStatusCode Status {
        get;
        internal set;
      }
    }
  }

  internal interface ISignInImpl {
    Future<GoogleSignInUser> SignIn();
    Future<GoogleSignInUser> SignInSilently();
    void EnableDebugLogging(bool flag);
    void SignOut();
    void Disconnect();
    void Configure(GoogleSignInConfiguration configuration);
    }
}  // namespace Google