Gazebo 5 doesnot load customized object

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Hi

Gazebo 5 screen becomes dark for a while then back to normal, when selecting a customized object ( segment of Pavement) that has been transformed from Sketchup model to .dae via Blender 3D, and no object will be exported to the current environment. I think i have done something wrong with the SDF file of the model. My model directory in the gazebo models' directory has : 1- meshes folder that contains the .dae file. 2- materials folder that have three images in 'textures' folder coming from Blender exportation process of the .dae file. 3-model.config file 4- model .sdf file. here is the SDF file:

 <?xml version="1.0" ?>
<sdf version="1.4">
 <model name="Ground Road">
<static>true</static>
<link name="link">
  <collision name="collision">
    <geometry>
      <mesh>
        <uri>model://test/meshes/Nstreet.dae</uri>
        <scale>1.5 1.5 1.5</scale>
      </mesh>
    </geometry>
  </collision>
  <visual name="visual">
    <geometry>
      <mesh>
        <uri>model://test/meshes/Nstreet.dae</uri>
         <scale>1.5 1.5 1.5</scale>
      </mesh>
    </geometry>
  </visual>
</link>

</model> </sdf>

ps: I tried adding<scale>1.5 1.5 1.5</scale> and nothing changed .

any help?