I just had this problem. What actually helped me was deleting the .suo file in the same directory of .uproject.
It was a misconfiguration of Visual Studio (That happened when I was switching engine versions).
I hope it helps! 
I just had this problem. What actually helped me was deleting the .suo file in the same directory of .uproject.
It was a misconfiguration of Visual Studio (That happened when I was switching engine versions).
I hope it helps!