Blur Shader Not Working in SinglePass (for VR)

Unity Engine
,
1

I’m trying to run the following shader in single pass but results in a gray/black screen. It works fine in multi-pass.

I’m using the built in render pipeline.

Shader "Hidden/BlurEffectConeTap" {
    Properties { _MainTex ("", any) = "" {} }
    CGINCLUDE
    #include "UnityCG.cginc"
    struct v2f {
        float4 pos : SV_POSITION;
        half2 uv : TEXCOORD0;
        half2 taps[4] : TEXCOORD1;
    };
    sampler2D _MainTex;
    half4 _MainTex_TexelSize;
    half4 _MainTex_ST;
    half4 _BlurOffsets;
    v2f vert( appdata_img v ) {
        v2f o;
        o.pos = UnityObjectToClipPos(v.vertex);
        o.uv = v.texcoord - _BlurOffsets.xy * _MainTex_TexelSize.xy;
#ifdef UNITY_SINGLE_PASS_STEREO
        // we need to keep texel size correct after the uv adjustment.
        o.taps[0] = UnityStereoScreenSpaceUVAdjust(o.uv + _MainTex_TexelSize * _BlurOffsets.xy * (1.0f / _MainTex_ST.xy), _MainTex_ST), _MainTex_ST);
        o.taps[1] = UnityStereoScreenSpaceUVAdjust(o.uv - _MainTex_TexelSize * _BlurOffsets.xy * (1.0f / _MainTex_ST.xy), _MainTex_ST), _MainTex_ST);
        o.taps[2] = UnityStereoScreenSpaceUVAdjust(o.uv + _MainTex_TexelSize * _BlurOffsets.xy * half2(1, -1) * (1.0f / _MainTex_ST.xy), _MainTex_ST);
        o.taps[3] = UnityStereoScreenSpaceUVAdjust(o.uv - _MainTex_TexelSize * _BlurOffsets.xy * half2(1, -1) * (1.0f / _MainTex_ST.xy), _MainTex_ST);
#else
        o.taps[0] = o.uv + _MainTex_TexelSize * _BlurOffsets.xy;
        o.taps[1] = o.uv - _MainTex_TexelSize * _BlurOffsets.xy;
        o.taps[2] = o.uv + _MainTex_TexelSize * _BlurOffsets.xy * half2(1,-1);
        o.taps[3] = o.uv - _MainTex_TexelSize * _BlurOffsets.xy * half2(1,-1);
#endif
        return o;
    }
    half4 frag(v2f i) : SV_Target {
        half4 color = tex2D(_MainTex, i.taps[0]);
        color += tex2D(_MainTex, i.taps[1]);
        color += tex2D(_MainTex, i.taps[2]);
        color += tex2D(_MainTex, i.taps[3]);
        return color * 0.25;
    }
    ENDCG
    SubShader {
         Pass {
              ZTest Always Cull Off ZWrite Off
              CGPROGRAM
              #pragma vertex vert
              #pragma fragment frag
              ENDCG
          }
    }
    Fallback off
}