Why can't i share a file with other applications on iPhone?

I'm trying to open a file to be linked to another app (Instagram) on my iPhone. I edit this video file so i'm not getting it directly from my camera roll, but i have a link to it locally which i've logged on my physical device below:

uri:

"private/var/mobile/Containers/Data/Application/(Long filename).mp4"

What i'm trying to to with this is:

shareToApp = (uri) => {
        amendedURI = 'file://' + uri;       
        let encodedURL = encodeURIComponent(amendedURI);  
        let instagramURL = 'instagram://library?AssetPath=${' + encodedURL + '}';
        return Linking.openURL(instagramURL);
}

but the screen where you share to 'Feed' or 'Stories' doesn't display my video.

Is there something in the uri path which prevents me from achieving this?