Sorry about inconvenience caused. There is a Shopify ongoing issue at the moment which is causing this behavior. This has nothing to do with the app.
Shopify is currently having issue with assets/extensions URL where they are throwing 404 error due to which your content isn't being loaded on a page.
We've already raised this to Shopify and they are looking into it. This is affecting most of the merchants and apps at the moment who makes use of app blocks. Additionally, we've also raised this to Shopify community portal & Slack to get maximum attention. Once we have an update from Shopify, we will get back to you.
From technical standpoint, Shopify holds extensions assets URL behind their CDN and they are having issue serving them.
Community post: https://community.shopify.com/c/shopify-apps/app-embed-extension-blocks-url-throwing-404/m-p/2467784#M75154
