project type incompatible in visual studio

I have just reinstalled windows on my pc, installed visual studio community 2015, installed unity 5.5 and set unity to use visual studio as the code editor. However, when I double click a script in unity to open it, visual studio refuses to open the project (though I can still edit the script, just without any features like code highlighting/completion), saying that it’s incompatible with this version of visual studio. The same project works fine on my laptop (also windows 10, unity 5.5 and VS community 2015). What is the problem and how can I fix it?

86286-unity-vs-project-error.png

Have you downloaded “Visual Studio Tools for Unity?”