hmta api newsletter error

gistfile1.js

// the end point im hitting is https://lyricgen.hmtaapi.com/api/v1/newslettercontacts/
// it returns the current list but doesnt update it. 
// if i try and update something even on the site( https://lyricgen.hmtaapi.com/api/v1/newslettercontacts/)  such as 
// { first_name: 'luke', newsletter: 1,} it returns a server error  

async saveAndCloseOutNewletter() {
    const { firstName, lastName, email } = this.state;
    const body = {
      first_name: firstName,
      last_name: lastName,
      email_address: email,
      newsletter,
    };

    try {
      const res = await axios.post(
        newsletterApi,
        body,
      );
      console.log(res);
    } catch (e) {
      console.log(e, 'error');
    }
  }