Search Console error with sitemap - Help?

My website has been active for less than 1 month and I have been checking how the indexing is going. So far I have some categories, pages, etc. but not half of the posts I have published.

It is all linked to the central page and the posts between them. Basically, I have done everything that you are supposed to do and obviously, I don't mind waiting weeks/months, I know that this process can take longer.

But since yesterday I see this problem in my sitemap. I have read that it may be a bug error so I have re-entered the URL of my sitemap and it appears exactly the same as in the old one, basically "Couldn't fetch" in the most important parts which are the pages and post.

Any idea what I can do?

(It won't let me include a photo but it basically says "Success" in the categories and tags, and "Couldn't fetch" in pages and posts.)