Setting up a database using Volley - getParams() never gets called

I have been following this tutorial to make a simple login / register database: http://ift.tt/1gfNOBZ

For some reason, when I try to log in or register I always get this error:

E/Volley﹕ [16019] BasicNetwork.performRequest: Unexpected response code 403 for http://192.168.... 

So I started to debug, and noticed that getParams() (used to insert data into the database) never gets called. Here is the method I'm using to register users:

private void registerUser(final String name, final String email,
                              final String password) {

        StringRequest strReq = new StringRequest(Request.Method.POST,
                AppConfig.URL_REGISTER, new Response.Listener<String>() {

            @Override
            public void onResponse(String response) {
                Log.d(TAG, "Register Response: " + response.toString());

                try {
                    JSONObject jObj = new JSONObject(response);
                    boolean error = jObj.getBoolean("error");
                    if (!error) {
                        // User successfully stored in MySQL
                        // Now store the user in sqlite
                        String uid = jObj.getString("uid");

                        JSONObject user = jObj.getJSONObject("user");
                        String name = user.getString("name");
                        String email = user.getString("email");
                        String created_at = user
                                .getString("created_at");

                        // Inserting row in users table
                        db.addUser(name, email, uid, created_at);

                    } else {

                        // Error occurred in registration. Get the error
                        // message
                        String errorMsg = jObj.getString("error_msg");
                        Toast.makeText(getActivity().getApplicationContext(),
                                errorMsg, Toast.LENGTH_LONG).show();
                    }
                } catch (JSONException e) {
                    e.printStackTrace();
                }

            }
        }, new Response.ErrorListener() {

            @Override
            public void onErrorResponse(VolleyError error) {
                Log.e(TAG, "Registration Error: " + error.getMessage());
                Toast.makeText(getActivity().getApplicationContext(),
                        error.getMessage(), Toast.LENGTH_LONG).show();
            }
        }) {

            @Override
            protected Map<String, String> getParams() {
                // Posting params to register url
                Map<String, String> params = new HashMap<String, String>();
                params.put("tag", "register");
                params.put("name", name);
                params.put("email", email);
                params.put("password", password);

                return params;
            }

        };

        // Adding request to request queue
        AppController.getInstance().addToRequestQueue(strReq, tag_string_req);
    }

Does anyone know why this may be happening? I have already sweat 8 pints and probably grew a couple grey hairs trying to figure this out - any help is HIGHLY appreciated.

Thanks in advance for any insight! Please let me know if any more information is needed.