Two different jobs, one word
"Installing the pixel" usually means someone pasted the base Meta Pixel snippet into the site's header code. That step alone does almost nothing for your ads. It can register a page view if it's placed correctly — that's it.
The part that actually makes a campaign work is custom events: the code that fires when someone adds to cart, starts checkout, submits a lead form, or completes a purchase. That's a separate, deliberate step. It has to be wired to the specific action on the specific page, tested, and confirmed. Skipping it is easy to do by accident — the base snippet "working" gives everyone false confidence that the job is done.
The exact test — don't skip any step
Visit your site with it active. It should show a green checkmark and your pixel ID on every page. Gray or nothing means the base pixel itself isn't firing — stop here, that's the more serious problem.
This is the real source of truth, not the Pixel Helper alone. Load your site with Test Events open. You should see PageView events land in real time. "No activity in the last 48 hours" means the base install has a problem, regardless of what anyone told you about it.
Add a product to cart. Submit the lead form. Go through a real (or test-mode) purchase. Watch Test Events for the matching custom event — AddToCart, Lead, Purchase, whichever applies. If PageView shows up but the actual conversion event never does, the base pixel is fine and the custom events are the gap.
Some site builders and plugins fire a generic event automatically but never map it to Purchase or Lead specifically. Check the event name in Test Events matches what your campaign will actually optimize toward — a "CustomEvent" that isn't named correctly won't help your ad set learn anything.
Why this is worth checking before you launch anything
A campaign aimed at conversions — sales, leads, checkouts — needs conversion data to optimize against. No custom events means Meta's algorithm has nothing to learn from except "who visited the page," which isn't the audience you're trying to reach. You end up paying to show ads to a cold audience with zero feedback loop telling the system who actually buys.
This matters even more if you're running a funnel with stages — top of funnel for awareness, then retargeting, then a bottom-of-funnel sales push. Pushing straight to the bottom-of-funnel, sales-focused stage without working event data isn't a shortcut. It's spending the same budget you'd spend building an audience properly, except with nothing to show for it afterward.