The algorithm might have information on why your ASIN has changed to an ineligible status and how to remedy this.
We recommend you reach out to Amazon support to get an answer as to why your ASIN is not eligible for advertising. Here are a few reasons your product might be ineligible:
Your product ran out of stock
Your product is not winning the buy box
My product is out of stock
When a product is out of stock, the product will become ineligible for advertising.
There is no need to exclude it from the strategies, because No money will be spent on it. This is an Amazon feature, which is native to the Advertising Console.
When the product is back in stock, the advertising will start to run again, assuming the product wasn’t excluded from the active strategies.
My ASIN's status is not winning the buy box
The product being advertised is not the BuyBox winner. If you're an Amazon seller, Amazon will not run your Sponsored Product ads unless you are winning the BuyBox. If you're a Vendor, Amazon will not run your Sponsored Product ads unless Amazon is winning the BuyBox.
To get your ads running again, try to win the BuyBox back. Amazon determines the BuyBox winner by weighing a number of factors including price, fulfilment, order defect rate, seller rating, and more.