"No network devices available" when wireless previously worked. (14.04)

Solution 1:

You do not have linux-image-extra for the running kernel 3.13.0-59. The kernel module ath9k is not installed. That is probably because the upgrade had been interrupted.

You need to connect to the internet by wire and run

sudo apt-get update
sudo apt-get dist-upgrade

If that does not install the extras, you can manually install them by

sudo apt-get install linux-image-extra-3.13.0-59-generic

but this means that some dependencies are not correct.

If you can't connect by wire, then boot with one of the previous kernels using grub menu. The wifi should work.

Then run the same commands.

Another option is to switch to 3.19 kernel by running

sudo apt-get install linux-generic-lts-vivid