Why is my facebook pixel code not showing on some browsers?

I need some urgent help please?
I added some facebook pixel code to a site http://electricbicycle.com.au
i added it to the child theme header and it seems to on;y appear on windows chrome?
Its not visible on any mac browsers, but you can see it on google chrome - see picture attached.
What on earth is going on?
Why, why would this NOT be showing everywhere but only on chrome?
LVL 11
Amanda WatsonWeb DeveloperAsked:
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David FavorLinux/LXD/WordPress/Hosting SavantCommented:
Trying installing https://developers.facebook.com/docs/facebook-pixel/pixel-helper into Chrome to debug Facebook pixel problems.

Currently the debugger shows your page contains no Facebook pixel.

If you do a View Source on the page, you'll also see there's no Facebook pixel on your page.
Lucas BishopClick TrackerCommented:
I see the following plugin is running on your site:
<!-- Performance optimized by W3 Total Cache. Learn more: https://www.w3-edge.com/products/

Open in new window

Have you refreshed the page cache? Could be that you're simply viewing the old version of the page.

In the plugin interface it should look something like this:
empty cache

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Amanda WatsonWeb DeveloperAuthor Commented:
That was it
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