I can't see the model as 3D gray. How can I fix?

Hi. I’m trying to make donuts by following blender guru. right now -I don’t know why- I can’t see the model as I marked in the red on the left. caused? Where did I turn it off, anyone have any guesses?

hi,

top right viewport press this Icon
image

if you have installed the PieMenu …

https://docs.blender.org/manual/en/latest/addons/interface/viewport_pies.html

then press Z and switch

advanced ! choose how the object should display in the viewport here :

happy donuting

oh! thank you so much Walter. i thought it was a very simple thing, but because I am a beginner, it was difficult.