Your company is currently in the process of setting up data pipelines for their marketing campaigns. An essential business requirement for processing Google Cloud Pub/Sub streaming data involves periodically identifying the inputs and their respective timings during the campaigns. Engineers have opted to utilize windowing and transformation functionalities within Google Cloud Dataflow to fulfill this requirement. However, during testing, they encounter a failure in the Cloud Dataflow job for all streaming inserts. What is the most probable cause of this issue?