Your custom event in GTM is firing in preview but not reliably showing in Meta due to:
- Pixel base code fires after the event → event is lost
- Wrong fbq('trackCustom') format
- Triggers not matching live page
- Consent issues or blockers (cookies, iOS, ad blockers)
- Tag fires too early—use “Window Loaded”
Fix It Checklist:
- Make sure your Meta Pixel base code is firing before the custom event.
- Use Custom HTML tag with fbq('trackCustom', ...) syntax.
- Set the tag to fire on Window Loaded to ensure Meta Pixel has initialized.
- Avoid relying only on preview; check real data in Meta Events Manager.
- Temporarily turn off cookie banners or blockers while testing.
- Use Test Events tool in Events Manager with a Test Code added to GTM: