My render is black and all of the fixes I have seen do not work I am following Blender Guru's donut tutorial on Youtube, and it was working fine until I started doing the coffee. Now, whenever I go into the render viewport the screen is completely black. Whenever I hide the donut and only render the coffee it works fine. What is the problem? None of the fixes I have found have worked.
It's not the donut - it's the material you are using. Whenever I choose other material the scene renders just fine, but with material nomber 3 and 6 everything goes black. 
It has to do something with the nodes you are using because when "Use nodes" is checked - it's black and when it's not checked it's normal.




My advice is not to use these materials - make a new one. You can even make the same nodes but don't capy and paste them - folow Andrew's tutorial.