Stencil Buffer working in scene view but black in game view.

I'm working on a VR game right now and the team consists of only programmers (student project) so I was thinking of making circular windows using a stencil test, however, it's working in Scene view but gives black circle in game view instead of the skybox. Can anyone help me in fixing this please ?

Mask Shader for the cylinder :

 Shader "Stencil/CircularWindow"
 {
     Properties
     {
         _MainTex ("Texture", 2D) = "white" {}
     }
     SubShader
     {
         Tags { "RenderType"="Opaque" }
         LOD 100
         ColorMask 0
 
         Pass
         {
 
             Stencil
             {
                 Ref 2
                 Comp always
                 Pass replace
             }
 
             CGPROGRAM
             #pragma vertex vert
             #pragma fragment frag
             #include "UnityCG.cginc"
 
             struct appdata
             {
                 float4 vertex : POSITION;
                 float2 uv : TEXCOORD0;
             };
 
             struct v2f
             {
                 float2 uv : TEXCOORD0;
                 float4 vertex : SV_POSITION;
             };
 
             sampler2D _MainTex;
             float4 _MainTex_ST;
             
             v2f vert (appdata v)
             {
                 v2f o;
                 o.vertex = UnityObjectToClipPos(v.vertex);
                 o.uv = TRANSFORM_TEX(v.uv, _MainTex);
                 return o;
             }
             
             fixed4 frag (v2f i) : SV_Target
             {
                 // sample the texture
                 fixed4 col = tex2D(_MainTex, i.uv);
                 return col;
             }
             ENDCG
         }
     }
 }

Stencil Test shader for the wall :

 ![Shader "Stencil/WindowWallShader" {
     Properties {
         _Color ("Color", Color) = (1,1,1,1)
         _MainTex ("Albedo (RGB)", 2D) = "white" {}
         _Glossiness ("Smoothness", Range(0,1)) = 0.5
         _Metallic ("Metallic", Range(0,1)) = 0.0
     }
     SubShader {
         Tags { "RenderType"="Opaque" }
         LOD 200
 
         Stencil
         {
             Ref 2
             Comp NotEqual
             Pass keep
         }
 
         CGPROGRAM
         // Physically based Standard lighting model, and enable shadows on all light types
         #pragma surface surf Standard fullforwardshadows
 
         // Use shader model 3.0 target, to get nicer looking lighting
         #pragma target 3.0
 
         sampler2D _MainTex;
 
         struct Input {
             float2 uv_MainTex;
         };
 
         half _Glossiness;
         half _Metallic;
         fixed4 _Color;
 
         // Add instancing support for this shader. You need to check 'Enable Instancing' on materials that use the shader.
         // See https://docs.unity3d.com/Manual/GPUInstancing.html for more information about instancing.
         // #pragma instancing_options assumeuniformscaling
         UNITY_INSTANCING_BUFFER_START(Props)
             // put more per-instance properties here
         UNITY_INSTANCING_BUFFER_END(Props)
 
         void surf (Input IN, inout SurfaceOutputStandard o) {
             // Albedo comes from a texture tinted by color
             fixed4 c = tex2D (_MainTex, IN.uv_MainTex) * _Color;
             o.Albedo = c.rgb;
             // Metallic and smoothness come from slider variables
             o.Metallic = _Metallic;
             o.Smoothness = _Glossiness;
             o.Alpha = c.a;
         }
         ENDCG
     }
     FallBack "Diffuse"
 }][1]

[1]: /storage/temp/114060-gameview.png