My dating site used to index for some keywords on the first page. I usually write articles and promote these key words for a few months. Now, they are not indexed on Google anymore.

Does Google de-index for promoting same keywords many times?

How do I change the way to get these keywords indexed again?

Thanks veyr much.

The search engine doesn't index keywords. It indexes web pages.

Maybe what you mean is over-optimized keywords, if yes then it will affect your serps on Google. Make sure your keyword density is under 3%.