If you have submitted a request in GSC to index the pages of your website but nothing has happened, the first thing you should do is simply wait. Sometimes the process just takes longer than expected.
If, even after a significant amount of time, your pages still are not ranking or being indexed (which are not the same thing), then based on my experience the reasons usually fall into one of two categories:
First, there may be certain blocks preventing Google from crawling or indexing your pages (for example - in robots.txt).
Second, and much more commonly, the issue is weak content. Content that is not original, content that is low quality, often AI-generated, and therefore not the type of material Google wants to index, let alone rank.