[Matter Control] SketchUp icon will not appear in Matter Control queue ... why?

I am New to Sketchup and matter Control. My 3D printer systems works. However, the Icon in Matter Control will no longer appear in the Matter Control queue (like it once did) when I load the file from the folder it was saved in .
Thanks for any help.

This appears to be a question about Matter Control, not about SketchUp. They are separate products. You should post your question to their discussion forum.