Quick Answer
When Shopify PMax is not working, run five checks in sequence: feed disapproval rate, brand cannibalization percentage, audience signal presence, asset group theming, and conversion signal integrity. The first check that fails is usually the dominant cause. Fix it, measure for two weeks, then re-run.
Checks 1-2: Feed and brand
Feed disapproval rate above 10 percent means catalog exposure is suppressed; fix feed first. Brand search impression share inside PMax above 2 percent means brand cannibalization; add brand negatives before any other optimization. Quantifying the cannibalization share before scaling spend is the diagnostic step most accounts skip; the brand-search audit walks the two-week incrementality test and the PMax brand-exclusion fix.
Checks 3-4: Audiences and themes
No customer list uploaded: upload it now. Asset groups themed by creative format (videos vs images) instead of product segment: re-theme by margin and category. These two fixes alone recover significant performance in most accounts.
Check 5: Conversion signal
Conversion fires on add-to-cart instead of order-received: fix the tag. Value does not pass: add it. GA4 and Ads double-counting: deduplicate. Corrupted conversion signal cannot be compensated for by any bid or creative optimization. For the prior question of whether Google Ads is even the right primary platform for the store, see the Google Ads versus Meta Ads for ecommerce comparison.
Common Questions
On record.
How long should I wait before declaring PMax not working?
Six to eight weeks of learning with stable inputs. Inside that window, performance fluctuation is expected. Past that window, structural diagnostic is warranted.
Can I pause PMax and restart fresh?
Pausing loses learning. Fix in place; the algorithm recalibrates faster than a restart rebuilds.
What if multiple checks fail simultaneously?
Order by impact-to-effort. Feed fix is usually first (highest impact, moderate effort). Brand negatives is second (moderate impact, low effort). Continue from there.
Is Performance Max ever the wrong campaign type for a Shopify store?
For stores below roughly 30 conversions per 30 days, PMax cannot train bid strategies. Manual CPC Shopping is the correct structure below that volume threshold.
Should I hire an agency to fix this or diagnose first?
Diagnose first. The Conversion Second Opinion identifies which layer has failed; hiring decisions follow the diagnostic, not the other way around.
The Engagement Format
Begin with the diagnosis. Not the proposal.
$999 · 72-hour written diagnostic · No retainer structure · fee is final on submission before work commences
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