A new delivery rings on your driver's phone until he opens it. If he says he did not hear a job, go through these steps with him.
Step 1. Go on duty
He turns on the switch at the top of his deliveries screen so it reads On duty.
Step 2. Allow notifications
When the phone asks whether the app may send notifications, he allows it.
Without this permission, new deliveries still reach his list, but his phone cannot alert him while the app is closed.
If he refused before, he opens his phone's settings, finds Storedoor Driver, and turns notifications on.
Step 3. Open the delivery to stop the ring
When a delivery arrives, the phone rings. With the app open he also sees New delivery for you. He opens the delivery and the ring stops. When you press Mark Ready on one of his orders, he also sees An order is ready for collection.