cannot get copied code value though the RPA process

I am new to Appian. I cannot get the test result: :the cage field in the RPT_CAGE_Info variable contains the CAGE string returned by the robotic task   after finished the step "Add the Execute Robotic Task node" in the process model which is the step before "Add an XOR gateway" when following online training docs.appian.com/.../tutorial-retrieval-process.html .  I have checked all possible causes, but no idea. Your advices and suggestions how to debugging are very appreciated! 

This is the result I got in PM history