The following requirements must be met for embedded apps to load in
When merchants try and access apps which have not been updated, they will be redirected to the old admin domain in a new tab. They will also be shown a banner letting them know that they've been redirected in the original tab.
If you have recently updated your app, or if you are unsure if your app has ever loaded correctly within the new admin domain, you are encouraged to test the app on any partner owned dev store. If you are redirected, ensure that your app has loaded correctly under the banner on admin.shopify.com. We will record the successful load, and within 3 hours our data pipeline will update. Once the pipeline has updated, the banner/redirect will no longer occur.