Fix Shopify Checkout Pixel Tracking

My Shopify store works fine for customers, but from the data side it’s broken: the purchase-tracking pixel never fires on the checkout thank-you page. Because of this functionality issue I can’t see conversions in Meta Events Manager or Google Analytics, and my ad optimisation is flying blind.

Here’s what I need from you:
• Audit the current theme, checkout.liquid (or post-purchase extension) and any GTM or Facebook Pixel snippets to locate the conflict.
• Repair or re-install the purchase pixel so it triggers once—without duplicates—on every successful order.
• Verify the fix in real time with the Facebook Pixel helper / Meta Events Manager and, if relevant, GA4 debug view.
• Hand over a brief note explaining what you changed so I can maintain it after theme or app updates.

If you’ve solved similar checkout-tracking problems in Shopify before and are comfortable with Liquid, Shopify Scripts, GTM and Meta’s pixel, I’d like to get this wrapped up quickly.