Children perspective 3D effect not working

I was working through the Design Portfolio Course when I got stuck on the 3D password grid.

I followed the video step by step, but I couldn’t go beyond the camera effect and moving the “password cell color” divs along the Z axis. No matter what value I entered, the div blocks did not change along the Z axis. I’m not sure where I went wrong because I restarted and still got stuck at the same position.

Could someone please put me in the proper path or explain what I’m doing wrong? I truly want to understand how the effect was created and be able to replicate it properly.

Cheers.