Google Analytics Global Site Tag (gtag.js) for Facebook Instant Articles

gtag4fbia.js

<!-- Global site tag (gtag.js) - Google Analytics -->
<script async="async" src="https://www.googletagmanager.com/gtag/js?id=UA-XXXXXXXX-X"></script>
<script>
  window.dataLayer = window.dataLayer || [];
  function gtag(){dataLayer.push(arguments)};
  gtag('js', new Date());

  gtag('set', 'page_title', 'FBIA: '+ia_document.title);
  gtag('set', 'campaignSource', 'Facebook');
  gtag('set', 'campaignMedium', 'Social Instant Article');

  gtag('config', 'UA-XXXXXXXX-X');
</script>

Same, not working

Check this out: https://stackoverflow.com/questions/50231721/how-to-track-utm-source-in-google-analytics-using-gtag

Do it this way:
gtag('set', 'campaign', { medium: '', source: '', name: '', content: '' }); // code to send pageview / event

Or if you are doing this with the initial page view:
gtag('config', ''UA-XXXXXXX-X', { campaign: { medium: '', source: '', name: '', content: '' } );