There are three possible reasons why the score will not improve despite adding your content with your guidelines:
1. Your competitors are dominated by one or two domain(s). We need at least 3 different domains to do the calculations.
You can get less than three needed domains when you, for example, run a query for a branded keyword, like in the example below:
2. SERPs are dominated by the pages we can't crawl. The most common example is when all results are PDF files.
3. If the Content Editor is very old. When your Content Editor was created before we introduced Content Score (July 2020), CS will be 0. Please, create a new Content Editor.