SolutionEngine.ERROR_0002 when displaying xaction in iframe

I made a xaction that displays a report. When I test it in design studio, the report displays perfectly.

When I put the url in an iframe however, I get SolutionEngine.ERROR_0002:
Debug: Start uitvoering van null/null/null (org.pentaho.platform.engine.services.solution.SolutionEngine)Fout: SolutionEngine.ERROR_0002 - Geen oplossing opgegeven (org.pentaho.platform.engine.services.solution.SolutionEngine)

What is the reason for these errors? I also get these errors when including the other xactions from the included examples.

Regards