stl files are not showing in rvis

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Hi! I'm using ros2 galactic I built a urdf file for my robot as showing here

using this URDF file

<?xml version="1.0"?>
<robot name="uiabot" xmlns:xacro="http://ros.org/wiki/xacro">

  <!-- Define robot constants -->
  <xacro:property name="base_width" value="0.315"/>
  <xacro:property name="base_length" value="0.325"/>
  <xacro:property name="base_height" value="0.075"/>

  <xacro:property name="wheel_radius" value="0.055"/>
  <xacro:property name="wheel_width" value="0.047"/>
  <xacro:property name="wheel_ygap" value="0.03"/>
  <xacro:property name="wheel_zoff" value="0.00"/>
  <xacro:property name="wheel_xoff" value="0.1"/>

  <xacro:property name="caster_xoff" value="0.11"/>

  <xacro:property name="imu_width" value="0.02"/>
  <xacro:property name="imu_length" value="0.03"/>
  <xacro:property name="imu_height" value="0.01"/>
  <xacro:property name="imu_yoff" value="-0.095"/>
  <xacro:property name="imu_xoff" value="-0.095"/>
  <xacro:property name="imu_zoff" value="0.0475"/>

  <xacro:property name="rplidar_yoff" value="0.0"/>
  <xacro:property name="rplidar_xoff" value="0.1"/>
  <xacro:property name="rplidar_zoff" value="0.1375"/>

  <!-- Robot Base -->
  <link name="base_link">
    <visual>
      <geometry>
        <box size="${base_length} ${base_width} ${base_height}"/>
      </geometry>
      <material name="Cyan">
        <color rgba="0 1.0 1.0 1.0"/>
      </material>
    </visual>
  </link>

  <!-- Robot Footprint -->
  <link name="base_footprint"/>

  <joint name="base_joint" type="fixed">
    <parent link="base_link"/>
    <child link="base_footprint"/>
    <origin xyz="0.0 0.0 ${-(wheel_radius+wheel_zoff)}" rpy="0 0 0"/>
  </joint>

    <!-- Wheels -->
  <xacro:macro name="wheel" params="prefix x_reflect y_reflect">
    <link name="${prefix}_link">
      <visual>
        <origin xyz="0 0 0" rpy="${pi/2} 0 0"/>
        <geometry>
            <cylinder radius="${wheel_radius}" length="${wheel_width}"/>
        </geometry>
        <material name="Gray">
          <color rgba="0.5 0.5 0.5 1.0"/>
        </material>
      </visual>
    </link>

    <joint name="${prefix}_joint" type="continuous">
      <parent link="base_link"/>
      <child link="${prefix}_link"/>
      <origin xyz="${x_reflect*wheel_xoff} ${y_reflect*(base_width/2+wheel_ygap)} ${-wheel_zoff}" rpy="0 0 0"/>
      <axis xyz="0 1 0"/>
    </joint>
  </xacro:macro>

  <xacro:wheel prefix="drivewhl_l" x_reflect="-1" y_reflect="1" />
  <xacro:wheel prefix="drivewhl_r" x_reflect="-1" y_reflect="-1" />

  <!-- Caster Wheel -->
  <link name="front_caster">
    <visual>
      <geometry>
        <sphere radius="${(wheel_radius+wheel_zoff-(base_height/2))}"/>
      </geometry>
      <material name="Cyan">
        <color rgba="0 1.0 1.0 1.0"/>
      </material>
    </visual>
  </link>

  <joint name="caster_joint" type="fixed">
    <parent link="base_link"/>
    <child link="front_caster"/>
    <origin xyz="${caster_xoff} 0.0 ${-(base_height/2)}" rpy="0 0 0"/>
  </joint>

  <!-- IMU -->
  <link name="imu_link">
    <visual>
      <geometry>
        <box size="${imu_length} ${imu_width} ${imu_height}"/>
      </geometry>
      <material name="Red">
        <color rgba="1.0 0 0 1.0"/>
      </material>
    </visual>
  </link>

  <joint name="imu_joint" type="fixed">
    <parent link="base_link"/>
    <child link="imu_link"/>
    <origin xyz="${imu_xoff ...