This happens sometimes for some reason.
It can be easily fixed in 16.04 by
sudo apt install linux-generic
This will install the correct kernel and the meta package for kernel upgrades.
Kernel did not upgrade between 14.04 LTS to 16.04 LTS
This happens sometimes for some reason.
It can be easily fixed in 16.04 by
sudo apt install linux-generic
This will install the correct kernel and the meta package for kernel upgrades.