EDIT: I solved this problem by using a WP Plugin, Add from Server. I figured it was something easy like that. Leaving the rest up below in case others have the same issue.
I’m an experienced WP user but have very little experience working with File Manager.
Site in question is http://ecomusicology.info
We hired an independent contractor to load our old site content fresh on a new WP build because the old site was compromised. Images are where they should be in the wp_content file which I can see using File Manager. However, not all the images are showing up when I click on Media in the WP Dashboard. This is an example of an image that is in the wp_content folder but not appearing in Media Library.
http://www.ecomusicology.info/wp-content/uploads/2017/02/P1060881.jpg
The image is loaded on our website (this post: https://ecomusicology.info/music-climate-and-therapy-in-kallawaya-cosmology-part-1/) but that’s only because it was already part of this page when it was loaded fresh on the new server.
I’m sure this is a relatively easy fix, would love any pointers!