Cycle Rendered Viewport Shading Models are flat grey?

I’m very new to blender and have begun to work on ‘the donut tutorial’ (for those who aren’t familiar: and was going fine until I made a new model (a coffee cup on a plate) and tried to see it in the Rendered viewport shading mode. All of the models in my scene were a completely flat grey colour with no texture or shadows. This is on 2.82.7 using cycles. The models don’t have any textures applied and the material preview works fine. Also, when I actually render the scene in this mode it renders perfectly.
I have no idea what I’ve done and I’d really appreciate some help!

Here are some pictures:

Did u try restarting blender. If it doesn’t work it is probably best to share your. Blend file for the people to figure out the problem.