Synopsis
Some software launched your script from which it expected a data return, but your script did not return any data.
Cause
You forgot to return some data in the REXX script by specifying it after the RETURN keyword.
Cure
Rewrite your REXX script to return data.
Cause
You're launching the REXX script with software other than Reginald's Script Launcher.
Cure
Use Script Launcher to run that REXX script.