JMeter - Could not find the TestPlan class

Question

I have a simple flume setup with a HTTP souce and a sink that writes the POST request payload to a file. (This complete setup is on a Linux machine).

After that my t

Answer 1

In testplan.jmx file contains:

  
    
    ...
    

That contains predefined variables. But sometimes when you save your testplan.jmx like "Save as" this section can be missed. For my case, answer from @Marged help me: "File > Save test plan as..."