As you are troubleshooting circuits, there are a few things that will become your friends.
Console Panel and Debug Component
Every component has a checkbox in the Standard Settings that enables sending output data to the console. Check that box to see what the components outputs in the Console Panel while a circuit runs.
You can also attach a Debug component to the output of any component to send that component's output to the Console Panel. Debug can be found in the Develop and Debug group in the Components List.
If the connector between 2 components and the outline of a component turn red during circuit execution, then there is an error. This will show up in the Errors Panel.
Errors usually indicate that something has been configured improperly and the circuit runner cannot understand how to execute a circuit.