Uncaught (in promise) TypeError: NetworkError when attempting to fetch resource. firefox url fetching issue

I made a form to collect email from users and give alert when data is successfully. When I enter any value in input, it gives me two errors:

1. Cross-Origin Request Blocked: The Same Origin Policy disallows reading the remote resource at http://localhost:3001/emailcoll. (Reason: CORS request did not succeed). Status code: (null)
2. Uncaught (in promise) TypeError: NetworkError when attempting to fetch resource.

How do I resolve it?

Below is code of function where the component is:

 const handleChange = (e) => {
    setFormData({
      ...formData,
      [e.target.name]: e.target.value,
    });
  };

  const handleSubmit = async (e) => {
    e.preventDefault();
    const response = await fetch('http://localhost:3001/emailcoll', {
      method: 'POST',
      mode:"no-cors",
      headers: {
        'Content-Type': 'application/json',
      },
      body: JSON.stringify(formData),
    });
    if (response.ok) {
      alert("Data Saved Successfully!")
    }
  };

below is code of form:

<form onSubmit={handleSubmit} className={styles.subs}>
    <label  className={styles.substext}>Stay updated on our all upcoming events!</label>
    <input onChange={handleChange} value={formData.email} name="email" className={styles.subsinput} placeholder="[email protected]"/>
    <button  type="submit" className={styles.subsbut}>Subscribe</button>
</form>

below is server code:

app.post('/emailcoll', async (req, res) => {
    const { email } = req.body;
    const filePath = './emailcoll.xlsx';

    let workbook;
    let worksheet;

    workbook = new ExcelJS.Workbook();
    await workbook.xlsx.readFile(filePath);
    worksheet = workbook.getWorksheet('Sheet 1');

    worksheet.columns = { header: 'Email', key: 'email' }
  
    worksheet.addRow({email});

   
    await workbook.xlsx.writeFile(filePath);
    res.send(STATUS_CODES)
})
app.listen(3001)

I tried using extensions for unblocking Access Control Allow Origin. Still same problem.
I have also included mode:”no-cors” in function.