Photoshop CC Automated Actions Fail

Have you tried re-recording the action from scratch?

I know this is an old thread, but I'm trying to learn scripting for Ps and also getting exact same message

Ps v22.0.1 on Win10
My script is:

var doc = app.activeDocument;
var indexedDoc = doc.duplicate('_tmpIndexed', true);


var indexedOptions = new IndexedConversionOptions();
indexedOptions.colors = 7;
/*indexedOptions.palette = Palette.LOCALSELECTIVE;
indexedOptions.forced = ForcedColors.NONE;
indexedOptions.transparency = false;
indexedOptions.dither = Dither.NONE;*/

indexedDoc.changeMode(ChangeMode.INDEXEDCOLOR, indexedOptions);

 Any insight?

I modified the following script to do the same thing as your action/batch (convert to working CMYK and overwrite the original files, it is presumed that the input file formats are capable of being saved as CMYK):

//forums.adobe.com/thread/2593940
//forums.adobe.com/message/10926314#10926314
#target photoshop  
var inFolder = Folder.selectDialog("Select the input folder", "");
var inFiles = inFolder.getFiles();
app.displayDialogs = DialogModes.NO;

for (var a = 0; a < inFiles.length; a++) {
    try {
        var inDoc = open(inFiles[a]);
        inDoc.changeMode(ChangeMode.CMYK);
        inDoc.save();
        inDoc.close();
    } catch (e) {
        continue;
    }
};
alert("Input files converted to working space CMYK and saved with embedded ICC profile");

https://prepression.blogspot.com/2017/11/downloading-and-installing-adobe-scripts.html

If your action does not have an open command step, you should not use the "override action open..." checkbox in the Batch interface.

I can not reproduce problem without more informations. Which version of Photoshop you are using? I am on Win running 21.0.1 version. Can you post screenshot with error message and Convert Mode step in action expanded. 

Moving to the Photoshop forum from Community Help