Images not resizing, even when sizes selected from media

So I’m just trying to implement a theme for a friend that he bought. Problem is that images aren’t resizing. Like if he has a product image that’s 1100px and you insert into a page and select medium (set to 300px) it still displays huge. You can see it here:
https://yeshivahuniforms.com/ the logo is so huge. I don’t really have time to go in and resize all of his images for him!

Has anyone else had this issue before?