Once the PWA is published, make sure the service worker and manifest.json are already there.
yoursite.com/manifest.json is the manifest file.
yoursite.com/firebase-messaging-sw.js is the service worker.
Once the app is there on Google playstore. Locate the "App Integrity" in Google playstore console and locate the SHA-256 fingerprint for your app. Copu and paste it in the asset links file, making sure that the package_name is correct.