Top reasons your PMax is spending but not converting could be,
1. Wrong or missing conversion tracking
Your pixel or GA4 setup might be broken or not firing properly.
If you're optimizing for a conversion event (like purchases or leads) and that event isn’t being tracked correctly, Google thinks you're getting zero results — so it keeps spending without learning.
Fix:
Go to Tools → Conversions → Diagnostics
Make sure:
The correct conversion action is set to “Primary”
Conversions are being recorded
There’s no tag misfiring or mismatch in destination URLs
Also, check Google Tag Assistant or Test Events in GA4 to confirm firing.
2. Final URL Expansion is taking users to the wrong pages
This is on by default. It can cause Google to send users to unrelated pages (like blog posts or careers pages), which kill conversion chances.
Fix:
Go to Campaign Settings → Final URL Expansion → Turn it off or restrict it to approved URLs.
3. Low-intent traffic from wrong placements
PMax runs across Search, Shopping, YouTube, Gmail, Display, etc. If your campaign is heavily leaning toward Display or YouTube, you might be getting cheap but irrelevant traffic.
Fix:
Check Insights tab → See which Search Themes, placements, and audiences are being matched. If irrelevant, your creative and audience signals need adjusting.
4. Too little data to optimize properly
PMax needs about 30–50 conversions per week to really learn. If your budget is too low or your event too far down the funnel (like purchase without intermediate steps), it might not have enough to work with.
Fix:
Consider optimizing for a higher-funnel event (e.g., add to cart, lead)
Or increase the budget temporarily to get it through the learning phase
5. Irrelevant or generic creative assets
If your headlines, images, or videos don’t match the audience’s search or intent, Google will match you to low-quality themes.
Fix:
Use clear, benefit-driven copy. Separate asset groups by intent or persona. Add strong value props and CTA.
Bonus tip:
Try running a standard Search campaign in parallel. This gives you more control and helps verify if the problem is PMax or just your overall funnel.