Why lspci could recognize 2 GPU but nvidia-debugdump only 1

There are 2 GPU in my computer
$ lspci | grep -i nvidia
02:00.0 VGA compatible controller: NVIDIA Corporation GP104 [GeForce GTX 1080] (rev a1)
02:00.1 Audio device: NVIDIA Corporation GP104 High Definition Audio Controller (rev a1)
03:00.0 VGA compatible controller: NVIDIA Corporation GP104 [GeForce GTX 1080] (rev a1)
03:00.1 Audio device: NVIDIA Corporation GP104 High Definition Audio Controller (rev a1)
but execute nvidia-smi failed,
$ nvidia-smi
Unable to determine the device handle for GPU 0000:03:00.0: Unknown Error
and from nvidia-debugdump --list, know that GPU 1 failed.
$ nvidia-debugdump --list
Found 2 NVIDIA devices
Device ID: 0
Device name: NVIDIA GeForce GTX 1080
GPU internal ID: GPU-08b994b4-1fec-e14b-012a-9f450cf55090

Error: nvmlDeviceGetHandleByIndex(): Unknown Error
FAILED to get details on GPU (0x1): Unknown Error

Why lspci could recognize 2 GPU but nvidia-debugdump only 1?