Try pressing the F7 key (it has a small airplane icon). This will turn Airplane mode on or off.
If this doesn't work, locate the small Novo button on the right side of the Yoga and press it to bring up a blue dialog box with 3 or 4 options. Although I own several Lenovos myself, I don't know exactly what options are available on your Yoga, but one option should be OneKey Recovery (provided you're running Windows). Selecting this option gives you the option to re-install Windows while allowing you to keep personal files.
If this doesn't work, either, there is a another option called System Recovery. This is a rather more drastic option that will completely wipe your computer and return it to its factory settings.