I dont know why my DataGrid MUI component is not working as intended

Im trying to use MUI (MaterialUI's React Component library) for the first time. I followed the installation process shown in documentation and im trying to use the DataGrid component in my React project.

Im trying to use the first example shown in the documentation page as a template.

My code:

import React from "react";
import { DataGrid } from "@mui/x-data-grid";

const columns = [
  { field: "id", headerName: "ID", width: 90 },
  {
    field: "firstName",
    headerName: "First name",
    width: 150,
    editable: true,
  },
  {
    field: "lastName",
    headerName: "Last name",
    width: 150,
    editable: true,
  },
  {
    field: "age",
    headerName: "Age",
    type: "number",
    width: 110,
    editable: true,
  },
  {
    field: "fullName",
    headerName: "Full name",
    description: "This column has a value getter and is not sortable.",
    sortable: false,
    width: 160,
    valueGetter: (params) => `${params.row.firstName || ""} ${params.row.lastName || ""}`,
  },
];

const rows = [
  { id: 1, lastName: "Snow", firstName: "Jon", age: 35 },
  { id: 2, lastName: "Lannister", firstName: "Cersei", age: 42 },
  { id: 3, lastName: "Lannister", firstName: "Jaime", age: 45 },
  { id: 4, lastName: "Stark", firstName: "Arya", age: 16 },
  { id: 5, lastName: "Targaryen", firstName: "Daenerys", age: null },
  { id: 6, lastName: "Melisandre", firstName: null, age: 150 },
  { id: 7, lastName: "Clifford", firstName: "Ferrara", age: 44 },
  { id: 8, lastName: "Frances", firstName: "Rossini", age: 36 },
  { id: 9, lastName: "Roxie", firstName: "Harvey", age: 65 },
];

const Paciente = () => {
  return (
    <div>
      {" "}
      <DataGrid
        rows={rows}
        columns={columns}
        pageSize={5}
        rowsPerPageOptions={[5]}
        checkboxSelection
        disableSelectionOnClick
      />
    </div>
  );
};

export default Paciente;

Its the exactly same code at the documentation. Now, what is happening:

Can someone help me with that?

Here's my package.json:

{
  "name": "junta-dashboard-2",
  "version": "0.1.0",
  "private": true,
  "dependencies": {
    "@emotion/react": "^11.8.2",
    "@emotion/styled": "^11.8.1",
    "@mui/material": "^5.5.2",
    "@mui/x-data-grid": "^5.6.1",
    "@testing-library/jest-dom": "^5.16.2",
    "@testing-library/react": "^12.1.2",
    "@testing-library/user-event": "^13.5.0",
    "@trendyol-js/react-carousel": "^2.0.1",
    "axios": "^0.26.0",
    "chart.js": "^3.7.1",
    "react": "^17.0.2",
    "react-chartjs-2": "^4.0.1",
    "react-dom": "^17.0.2",
    "react-draft-wysiwyg": "^1.14.7",
    "react-icons": "^4.3.1",
    "react-loading": "^2.0.3",
    "react-markdown-editor-lite": "^1.3.2",
    "react-markdownit": "^2.5.0",
    "react-quill": "^1.3.5",
    "react-router-dom": "^6.2.1",
    "react-scripts": "5.0.0",
    "styled-components": "^5.3.3",
    "web-vitals": "^2.1.4"
  },
  "scripts": {
    "start": "react-scripts start",
    "build": "react-scripts build",
    "test": "react-scripts test",
    "eject": "react-scripts eject"
  },
  "eslintConfig": {
    "extends": [
      "react-app",
      "react-app/jest"
    ]
  },
  "browserslist": {
    "production": [
      ">0.2%",
      "not dead",
      "not op_mini all"
    ],
    "development": [
      "last 1 chrome version",
      "last 1 firefox version",
      "last 1 safari version"
    ]
  }
}