How to get rid of "Could not load GPU driver" error?

Question

linux

Available onboard Ubuntu 16.04 with hybrid graphics.

00:02.0 VGA compatible controller: Intel Corporation 3rd Gen Core processor Graphics Controller (rev 09)
01:00.0 VGA compatible controller: NVIDIA Corporation GF108M [GeForce GT 635M] (rev a1)

Installed according to this manual.
Error when launching something via optirun

optirun gnome-terminal
[  516.638989] [ERROR]Cannot access secondary GPU - error: Could not load GPU driver

[  516.639029] [ERROR]Aborting because fallback start is disabled.

Specifying busid does not help. as everything was already specified in the configs correctly.
How to overcome?

Answer 1

/etc/bumblebee/bumblebee.conf Changed
to nvidia here?
Try rebooting bumblebeed