Troubleshooting Firebase App Check (Play Integrity) Blocking Requests on Internal Testing Builds

A developer is experiencing issues with Firebase App Check, specifically using the Play Integrity provider. While debugging directly from Android Studio with the Debug App Check Provider works correctly, release builds uploaded to the Play Store's Internal Testing track are resulting in 100% of requests being blocked as 'Unverified: invalid requests'. Logcat indicates that PlayCore is successfully requesting and receiving tokens. The developer has verified SHA-256 fingerprints for both upload and Play signing keys in Firebase and is seeking assistance to identify the cause of this discrepancy.