Instagram’s API only gives access to images at the largest size of 640px x 640px. Previously we could get 1080px x 1080px by guessing the URL path, but this was always a brittle technique and failed previously.
It looks like it is now impossible to guess the 1080px image URL so this feature won’t work going forward until a solution is found or Instagram expose the URL via the API.
Automatically Publish Instagram Media to WordPress
Intagrate is the best WordPress Instagram plugin for posting Instagram media to WordPress.