Referral API request headers CORS problem

Hi comminity,

I’m trying to use Yotpo’s API documentation to implement Yotpo’s referral into my test shopify store. It’s a pretty basic API implementation, but I’m getting into troubles as the reponse from Yotpo server is always a x-guid and x-api-key headers error.

This is the request I’m sending:

const handleReferral = () => {
    fetch(`https://loyalty.yotpo.com/api/v2/referral/share`, {
      method: "POST",
      headers: {
        'Content-Type': 'application/json',
        'Accept': 'application/json',
        'X-Guid': 'wuL**************4-XKA',
        'X-Api-Key': 'fMRdbg**************rAtt'
      },
      body: JSON.stringify({
        email: 'yotpo_test@yopmail.com',
        emails: 'yotpo_test_2@yopmail.com,yotpo_test_3@yopmail.com',
      })
    })
    .then(response => response.json())
    .then(resp => {
      console.log(`resp: `, resp);
    }).catch(e => {
      console.error(`Error: `, e);
    });
  }

so every single time I call to handleReferral() it returns the followin error:

Access to fetch at 'https://loyalty.yotpo.com/api/v2/referral/share' from origin 'https://tsa-test-preview.myshopify.com' has been blocked by CORS policy: Request header field x-guid is not allowed by Access-Control-Allow-Headers in preflight response.

POST https://loyalty.yotpo.com/api/v2/referral/share net::ERR_FAILED

So, as you can see it says always that the x-guid is now allowed by the server so it launches the CORS problem but based on the documentation this is the headers we need to send with the request.
I have to mention the credentials and emails I’m using are ok, but I don’t get this API working.

As a note: if I use Postman for checking the request it will work and still don’t know why.

Following I send some reference images of the error:

Thanks in advance.