When adding the remote, please make sure to select “NVIDIA SHIELD (Voice Remotes)” from the device list instead of the regular “NVIDIA SHIELD” option.
The (Voice Remotes) option uses BLE (Bluetooth Low Energy), which supports voice control.
The regular “NVIDIA SHIELD” option uses BT (Classic Bluetooth) — this only supports basic button controls and does not support voice input.
So simply choose the (Voice Remotes) version during pairing, complete the setup, and your voice control should work as expected.