Task com.google.firebase.a.v rejected from java.util.concurrent.ThreadPoolExecutor

There is a possibility that you are using a buggy version of firebase. After wasting 4 hours searching for a solution and learning about multi-threading in Android AGAIN! The final solution for me was to downgrade to another version.

For me, this version of dependency worked.

// Firebase
implementation 'com.google.firebase:firebase-core:16.0.8'
implementation 'com.google.firebase:firebase-database:16.1.0'