Some users reported Cortana stopped working soon after installing the Windows 10 Anniversary update.
- Press Windows Key + R to open Run window
- Type regedit to open Registry Editor
- Navigate to the key HKEY_CURRENT_USER\ SOFTWARE\ Microsoft\ Windows\ CurrentVersion\ Search
- On the right side look for BingSearchEnabled. Check the value. If the value is set to 0, then double click on the key and under value data, set the value as 1.
- Close the registry. Restart computer. Check if the problem is solved.