Only the latest post shows up on post page?

disclaimer: this is my first foray into wordpress

I'm creating a custom theme and in the single.php file, i have the main loop, however if i navigate to different posts, all that shows up is the latest post. I could go to the different permalinks, but the only post that shows up is the latest one. How do I make it so that the correct post shows up?

I tried changing the permalinks and deleting and adding pages, but I get the same result.