Does your website fulfill the intent of these keywords you currently don't have? If it does, try to add them somewhere on your page, preferably in H2, H3 headings or even in page title.
For example, let's say you're dealing with a SAaS website that is an AI CV generator. You have the keyword "AI CV generator" in your title, meta description and the body of your page and you are ranking for this keyword - all good.
But there is another keyword "AI CV maker" which is semantically the same as "AI CV generator" and the tool you have on your website is technically both a cv maker and a cv generator. But just because your page isn't optimized for the keyword "AI CV maker" - you have no ranking for it.
In such cases, you could try just adding the missing keyword to your page.
