Textures not appearing on object

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Hello, I'm trying to use a png of an aruco marker, but the textures don't appear. I have made a model of a square in the .gazebo folder, and I'm getting the model out, but when I'm trying to add textures to it it's just blank. I have tried to follow the standard grey wall model code, and even tried copy pasting most of it except for the file placements, still not getting any textures.

My sdf file:

<?xml version="1.0" ?>
<sdf version="1.5">
  <model name="trial">
    <static>true</static>
    <link name="link">
      <pose>0 0 1.4 0 0 0</pose>
      <collision name="collision">
        <geometry>
          <box>
            <size>7.5 0.2 2.8</size>
          </box>
        </geometry>
      </collision>
      <visual name="visual">
        <cast_shadows>false</cast_shadows>
        <geometry>
          <box>
            <size>7.5 0.2 2.8</size>
          </box>
        </geometry>
        <material>
          <script>
            <uri>model://trial/materials/scripts</uri>
            <uri>model://trial/materials/textures</uri>
            <name>vrc/marker</name>
          </script>
        </material>
      </visual>
    </link>
  </model>
</sdf>

Materials file:

material vrc/marker
{
    receive_shadows off
    technique
    {
        pass
        {
            texture_unit
            {
                texture grey_wall.png
                filtering anistropic
                max_anisotropy 16
                scale 1 1
            }
        }
    }
}

Config:

<?xml version="1.0"?>

<model>
  <name>Trial model</name>
  <version>1.0</version>
  <sdf version="1.5">model.sdf</sdf>

  <author>
    <name></name>
    <email></email>
  </author>

  <description>
    <p>ArUco Marker</p>
  </description>
</model>