Sponsored products not always showing in main SERPS

[whatson]

For some reason only about half the time my products are showing the Sponsored product results in the main SERPS, and when they are not showing, they are nowhere, not even #10 or 20, absolutely nowhere. But when they do show up, they are #1, 2 or 3 or some good position.

However, if you click on the shopping tab, to view shopping results, my products always show up there, like #1, 2 or 3, or again something high. It is just not consistently on the main SERPS.

I am using a PMAX campaign and have also tested it with shopping, and tried bidding higher as well.

Why could this be?

[clairemiso299]

Main SERP placements for Shopping ads are much more throttle based than the Shopping tab. Google only shows a small number of product ads in the core results, so it rotates advertisers to control ad load, page layout, and intent matching. Even strong products appear only when Google predicts a high click or conversion probability for that specific query at that specific moment.

If your items show consistently in the Shopping tab but not in the main SERP, it usually points to limited inventory for those top slots, intent shifts during the day, or PMax not winning the real-time auction for blended search placements.

Cleaning up product titles, tightening your feed attributes, and improving ROAS signals often increases how often you surface in the main SERP.