Network Manager not working: Disabled by Hardware Key

If Network Manager claims that Wifi is disabled by a hardware key, take these steps:
  1. Check if hardware keys disable the wifi (duh!) - this may include key combinations such as Fn-F2.
  2. Check rfkill list if some devices are blocked and unblock them with sudo rfkill unblock all
  3. If you have one blocked device, this may block all other devices due to a bug in Network Manager. Hence removing the modules of all other devices may be necessary to enable a device which is actually already unblocked. (e.g. sudo rmmod rf2800pci and sudo rmmod ideapad_laptop).
Worked for me - let me know how this works for you.