Gem_Low is transparent and not Blue.

Hi Ricardo aiidaiid ,

That's not a lot of information you give us here 😉. Let me make some guesses:

Are you by any chance using Blender 4.4? There the Face Orientation Overlay is Transparent instead of Blue (Red is still Red).

Also, make sure the Viewport Overlays are enabled.

For ALT+N to work, you need to be in Edit Mode and have the relevant Faces Selected.

And when you ask a question about something in a Lesson, it is always helpful to add a timestamp, so we know what you are talking about. And Screenshots can also help us troubleshooting.