CUDA 9.0 / GTX760 / Ubuntu 16.04 - Driver isn't working

I’ve followed the instructions on the Installation Guide…several times. I’ve purged the system of all things NVIDIA and started over…several times.

I cannot get my GTX760 to work on Ubuntu 16.04.

lspci | grep -i nvidia

returns:

01:00.0 VGA compatible controller: NVIDIA Corporation GK104 [GeForce GTX 760] (rev a1)
01:00.1 Audio device: NVIDIA Corporation GK104 HDMI Audio Controller (rev a1)

And then

dpkg -l | grep nvidia

returns:

ii  nvidia-384            384.90-0ubuntu0.16.04.2 amd64 NVIDIA binary driver - version 384.90
ii  nvidia-384-dev        384.90-0ubuntu0.16.04.2 amd64 NVIDIA binary Xorg driver development files
ii  nvidia-modprobe       384.81-0ubuntu1         amd64 Load the NVIDIA kernel driver and create device files
ii  nvidia-opencl-icd-384 384.90-0ubuntu0.16.04.2 amd64 NVIDIA OpenCL ICD
ii  nvidia-prime          0.8.2                   amd64 Tools to enable NVIDIA's Prime
ii  nvidia-settings       384.81-0ubuntu1         amd64 Tool for configuring the NVIDIA graphics driver

I’ve disabled secure boot, because that was causing issues previously, but no longer have any inclination as to what might be causing the issue.

When I run

./deviceQuery

I get:

./deviceQuery Starting...

 CUDA Device Query (Runtime API) version (CUDART static linking)

cudaGetDeviceCount returned 30
-> unknown error
Result = FAIL

Help, please. Thanks!