Synopsis
There was an invalid sub-keyword in an argument you supplied.
Cause
When passing some argument to an add-on library, Exit handler, or Environment, you supplied some sub-keyword/command that is not considered legitimate by the software.
Cure
Consult the documentation for that product to see what arguments you should be passing to a particular function/command that you're trying to use in that add-on library, Exit handler, or Environment. Look up this error message in that documentation. Check that you have the latest version of the software.