My models are black in the material preview and render view. The problem arised when I turned on my project. Everything worked before. I added the screenshot below.
$\begingroup$ This might sound strange, but every once in a while, when I load a scene (usually a very complex one), everything is black until I click the mouse around or pan the viewport a little. Have you tried selecting some things or moving the (view) camera? Also, you could try disconnecting the HDRI and reconnecting it to the world environment. Other than that, I don't know. $\endgroup$– Christopher BennettJul 18, 2020 at 6:52
$\begingroup$ Have you added a light to your scene? $\endgroup$– JonasJul 18, 2020 at 7:39
You probably opened the scene world and here is how to close it: at the top right you have 3 viewports and at the right of them, there is an arrow points down, click it and there should be scene lights and scene worlds. You need to close all of them. If your problem something like I think, that will solve it.
And btw you need to add lights to show colours on rendering.