Safari unable to load scripts from different domains on a website

I am trying to load Dropbox choose SDK on my website. But running in to an issue on Mac Safari browser.

```

<script async="" src="https://www.dropbox.com/static/api/2/dropins.js" id="dropboxjs" data-app-key="crbrplpove29sb2"></script>

```

but script doesnt load on xconvert.com (if you goto the network tab on https://www.xconvert.com/compress-mp4, it won't show dropins.js). I also tried manually injecting the script to the header once the page is loaded

```

const node = document.createElement('script');

node.src = 'https://www.dropbox.com/static/api/2/dropins.js';

node.type = 'text/javascript';

node.setAttribute('id', 'dropboxjs');

node.setAttribute('data-app-key', 'crbrplpove29sb2');

node.defer = true;

document.getElementsByTagName('head')[0].append(node);

```

But same code on other websites such as smallpdf and ilovepdf seem to work perfectly.

There is a preference on Safari, under Privacy saying 'Prevent cross-site tracking'. If I turn it off, then the script loads perfect on the xconvert. But that setting don't need to be turned off for other websites I meantioned above.

Any idea what may be causing this issue?

It almost like Apple whitelisted some website and block others from loading third-party scripts. Same thing happens if I try to load Google APIs as well. This only happens on Safari. It works fine on Chrome.

Safari version: 14.1.2

Mac version: 11.6

Following is the error thrown on script which is not much helpful