Thank you for your reply.
Strange, as this should not occur, as long as you are using the GUI scenario and if the required .jar file is present in its location.
BTW, have you tried to recreate the transformation scenario, as Radu suggested to the user who initially reported the same issue on this thread?
Could you try to recreate the transformation scenario associated with the DITA-OT transformation?
Basically, in the Configure Transformation Scenario(s) dialog, click New > DITA OT transformation > choose "WebHelp Classic" > OK. Apply the newly created scenario.
If this still not works, please try to download a fresh copy of the oXygen XML Editor v19 installation kit from the official download page (please follow this link
) and install it in a separate location (a folder different from the one you already have oXygen installed). Then retry running the WebHelp transformation scenario from the newly installed oXygen copy.
If everything else fails and you still obtain the same error, run the transformation and please send us the entire transformation log you obtain.