If you just integrated Haystack, it will take 24 hours for us to pull your last month's data. However, we wait till the weekend to pull the rest of your data due to API limitations.
However, if you are still missing some PRs, we suggest you take a look at our "Exclusions" page in the Haystack settings. On top of custom exclusion rules, you might have added, Haystack also automatically ignores bots.
Finally, PRs are also ignored if the author is not part of any Haystack team.