Custom image to instagram instead of post thumbnail

Hey!

Can I set custom image to post to instagram instead of the post thumbnail?

If I change the ;649 line in “class-woo-igp.php”

From:

$photoFilename = get_attached_file(get_post_thumbnail_id( $post_id ) );

To:

$photoFilename = 'https://xyz.com/123.jpg';

I get this error:
Dear user,
Your post ID 449 not posted on Instragram due to following reason.
Input file “https://xyz.com/123.jpg” doesn’t exist.

But the file exists at the provided link.