Here's how to get it back:
1. Run regedit
2. In Registry Editor, go to Computer\HKEY_LOCAL_MACHINE\SOFTWARE\Synaptics\SynTP\Defaults
3. Right click on white area on the right side, select New-> DWORD 32 Bit. Name it 2FingerTapAction.
4. Double click on your newly created 2FingerTapAction key and Enter 2 as the value, decimal.
See the image below for clarification.
4. Close Registry Editor
5. Restart your computer, and try the two finger tap on the desktop to see if the context option menu appears. It should be working.