Not sure if you tried this.
But first look at the Compute Shader in the Unity Editor and it may have a list of problems.
I had this same problem following the same blog and my fix was that unlike C#, in HLSL functions need to be made before you call them, and my Sphere() function was put after my Trace() function which called it. Hope this might have anyone with this issue.
P.S. Make sure you’re not using a URP(Universal Pipe Rendering) Project and if all else false sometimes just copying your asset folder to a new project works(this little trick has fixed the majority of my bugs in Unity).