I get error when ask PUT or POST request to Firebase RD when sending data javascript

I have a todo list where I want to store the todo tasks in a database under todo. But I get error. I have tried PUT and POST but same error. Why do I get this error? And how can I send data from input field to store in the database?

main.js

const form = document.getElementById('form')
const input = document.getElementById('input')
const todosUL = document.getElementById('todos')

const todos = JSON.parse(localStorage.getItem('todos'))
if(todos){
    todos.forEach(todo => addTodo(todo))
}


async function addTodoToFirebase() {
  try {
    const baseURL = 'https://todoparon-default-rtdb.europe-west1.firebasedatabase.app/'
    const url = baseURL + `todo.json`
    const response = await fetch(url)
    let data = await response.json()
    console.log(data)


    // Send the updated data back to Firebase
    const updateResponse = await fetch(url, {
      method: 'PUT', 
      body: input,
      headers: {
        'Content-type': 'application/json; charset=UTF-8',
      },
    });

    if (updateResponse.ok) {
      console.log('Data updated successfully in Firebase!');
    } else {
      console.error('Failed to update data in Firebase.');
    }
  } catch (error) {
    console.error('Error while updating data:', error);
  }
}

form.addEventListener('submit', (e) => {
    e.preventDefault()

    addTodo() 
    addTodoToFirebase()
    
})