Ubuntu 18.04 - cannot turn bluetooth on

Unblocking bluetooth using rfkill command solved this issue for me

First block bluetooth completely : rfkill block bluetooth

Then unblock it : rfkill unblock bluetooth

Note: If you don't have rfkill package installed in your system, then install it using sudo apt install rfkill.

Welcome to Ubuntu! I'm assuming you have the latest version 18.04, so first you need to find your Bluetooth settings which you can either go to via the main Settings menu, or direct from your panel search:

This will bring up your Bluetooth settings:

From here you can enable/disable Bluetooth. It will scan for any nearby devices, then you can click on them to pair.

If you have problems doing any of this, then it's likely that you've accidentally disabled the Bluetooth switch on your laptop, in which case it won't work in Windows either.

Update - try this:

sudo echo 'AutoEnable=true' >/etc/bluetooth/main.conf && /etc/init.d/bluetooth restart