Trouble updating material property from script with SetFloat

Hello, I am trying to update a variable in a custom texture from a c# script.

  Shader "UCLA Game Lab/Wireframe/Single-Sided"
         Properties
             {
                 _Color("Line Color", Color) = (1,1,1,1)
                 _MainTex("Main Texture", 2D) = "w$$anonymous$$te" {}
         
                 _TravelY("Travel Y", Float) = 0
         
             }
         
         SubShader
                 {
                     Pass
                     {
                         Blend SrcAlpha OneMinusSrcAlpha
                         LOD 200
         
                         CGPROGRAM
                         
                         #pragma target 5.0
                         #include "UnityCG.cginc"
                         #include "UCLA GameLab Wireframe Functions.cginc"
                         #pragma vertex vert
                         #pragma fragment frag
                         #pragma geometry geom
         
                         **float _TravelY;**
         
         // etc

Here's is my c#

 using System.Collections;
 using System.Collections.Generic;
 using UnityEngine;
 
 public class MoveController : MonoBehaviour
 {
     public Material heightMapX;
 
     
 
     public float speedX = 0f;
     public float speedY = 0f;
 
 
     // Start is called before the first frame update
     void Start()
     {
          //heightMapX.EnableKeyword("_travelX"); 
         heightMapX.SetFloat("_TravelX", speedX);
         heightMapX.SetFloat("_TravelY", speedY);
     }
 
     // Update is called once per frame
     void Update()
     {
 
         if (Input.GetKeyDown(KeyCode.UpArrow))
         {
             speedX += 5f;
             heightMapX.SetFloat("_TravelX", speedX);
         }
         if (Input.GetKeyDown(KeyCode.RightArrow))
         {
             speedY -= 5f;
             heightMapX.SetFloat("_TravelY", speedY);
         }
 
     }
 }

The value is updating in the inspector..for both the script variable and the shader property. But it doesn't update in the actual scene unless I manually change values in the inspector.

Truncated the shader code to make it easier to scan, so ignore the lack of corresponding variables.

Any idea why the scene isn't updating?