“Post Author” doesn’t show up on “Add New” screen

For some reason, the “Post Author” dropdown menu shows up when I edit an old post, but not when I’m creating a new one. I checked the Screen Options menu when in the Add New screen, and it’s not there either.

I thought the More Fields plugin might help, but when I got to the More Fields settings for the content type “Post,” it’s showing that “Post Author” is already enabled.

Any idea what’s going on and how I can add the “Post Author” dropdown to the “Add New” screen? It’s important because this is for a news site where an editor will frequently be the one posting a story that was actually written by someone else.

Thanks!