When using the downstream USB-C port located on the front of the UD-6950PDH to charge a connected iOS device such as an iPhone or iPad, first please verify that the dock is connected to a laptop host (using the rear host port), and that your iPad or iPhone is powered on and logged in.
Once the iPad or iPhone is plugged into the docks front USB-C port. Once the security prompt appears on the iPad or iPhone charging should also begin.