"Program not found" error message in ocamldebug

"[email protected] [ocaml_beginners]" <[email protected]> 26 Aug 2016 11:12:59 -0700

Newsgroups	gmane.comp.lang.ocaml.beginners
Message-ID	<[email protected]>

This short output says it all :

ocamldebug Optional/ladybird.out
    OCaml Debugger version 4.02.1

(ocd) run
Loading program... Program not found.

 This error message is not documented in the manual as far as I can see.
 How should I interpret the message ?
 

 Any help appreciated.