Bluetooth won't turn On on Ubuntu 20.04

I just experienced the exact same issue, always off in Gnome and no controller found. What do you see if you type the following in a terminal ?

dmesg | grep -i bluetooth

I had this log:

Bluetooth: hci0: Reading Intel version information failed (-110)

To resolve the problem, all I had to do was to perform a cold boot of my laptop.

Cf. comments in https://bugs.launchpad.net/ubuntu/+source/linux/+bug/1859592

I tried various hacks (all at once) and did a restart but I am not sure which led to the bluetooth working right.

I ran

sudo apt-get update
sudo apt upgrade
sudo systemctl start bluetooth
rfkill unblock bluetooth

And after the restart, it worked :?

This has happened to me before when I'd accidentally pressed the bluetooth on/off button on the laptop. (fn-F10 on my Thinkpad)