I’m not sure what your current Top of Search (TOS) percentage settings are, but based on what you described—if your ad used to show for a certain keyword and it no longer does—it’s likely a matter of increased competition.

If you're currently using a 100% Top of Search placement multiplier, I’d recommend testing higher—200% or even 300%—especially if you're in a competitive niche. Other sellers may be aggressively bidding for those top spots, which could be pushing you down in ad placement.

To break it down simply:

When you bid on a keyword in Amazon PPC, you're essentially paying for ad placement. For example, if you were bidding $1 for a keyword and used to get the top position, but now you're not, it likely means someone else is bidding higher—say $1.50 or $1.80—to win that top spot.

Amazon PPC is an auction system. So, if you're not adjusting your bids or TOS placement percentage in response to competition, you’ll likely lose visibility even if everything else in your campaign looks fine.

Since Amazon support has confirmed there's no issue with your campaign setup, it’s very possible that strategy, not structure, is where the gap is. There are several optimization techniques and strategic tweaks that can help improve performance.

Happy to dive deeper if you'd like help with that!