Instagram: no access to videos uploaded to Photos/Shared Folder

For work, I use my iPad to post to Instagram. When I add a video to Photos from my desktop, I also add it to a Shared Folder that I use for accessing photos from Instagram. However, Instagram cannot find the videos. I get a "No media. Photos and videos in your camera roll will appear here" message.

I have waited hours, turned airport mode on and off on the iPad, and also watched the videos in Photos on my iPad.

I've also noticed that videos I've taken on my phone (that are in Photos) will not show up in the Instagram app, either.

Has this happened to anyone else? Thank you!