Hi,
I installed my FB pixel on the thank you page snippet of the vendor like this:
<script> fbq('track', 'Purchase', { content_ids: 'fd-thank-you', });</script>
<!-- Facebook Pixel Code --><script> !function(f,b,e,v,n,t,s) {if(f.fbq)return;n=f.fbq=function(){n.callMethod? n.callMethod.apply(n,arguments):n.queue.push(arguments)}; if(!f._fbq)f._fbq=n;n.push=n;n.loaded=!0;n.version='2.0'; n.queue=[];t=b.createElement(e);t.async=!0; t.src=v;s=b.getElementsByTagName(e)[0]; s.parentNode.insertBefore(t,s)}(window, document,'script', 'https://connect.facebook.net/en_US/fbevents.js'); fbq('init', 'XXXXXXXXXXXXXXXXXXX'); fbq('track', 'PageView');</script><noscript><img height="1" width="1" style="display:none" src="https://www.facebook.com/tr?id=XXXXXXXXXXXXXXX&ev=PageView&noscript=1"/></noscript><!-- End Facebook Pixel Code -->
there are 2 parts of the pixel. 1st part is the main pixel and the second part is the event pixel.
https://adespresso.com/blog/facebook-pixel/
You need to make sure when you place the pixel you either use the JS or IMG part AND it has to contain your pixel ID so FB can locate which ad acct it's coming from.
Your vendor wasn't right this time, because the code you installed didn't contain your pixel ID so FB couldn't report the conversion back to you...