check /libs/dam/components/scene7/dynamicmedia/dynamicmedia_sly.js#470, you'd see that it requires 'imageserver' url/config and is configured to work in disabled mode
470 - contentPath = imageServer.replace("/is/image", "/is/content");
check if you've configured 'imageserverurl' property or otherwise remote assetpath and
use wcmmode=disabled to test on author. The code/docs have all you need.
snippet:
/**
* @param isWCMDisabled
* @return image server URL depending on WCM disabled
*/
function getImageServerURL(isWCMDisabled, assetPath, isRemote){
var imageServerURL = "";
if (isWCMDisabled) {
imageServerURL = properties['imageserverurl'];
}
else {
if(isRemote) {
// get publish server
var assetResource = resource.getResourceResolver().getResource(assetPath);
if (assetResource) {
publishRootPath = sling.getService(com.day.cq.dam.api.s7dam.utils.PublishUtils).getPublishNodeURL(assetResource);
return sling.getService(com.day.cq.dam.api.s7dam.utils.PublishUtils).externalizeImageDeliveryAsset(assetResource, "");
}
}
}
return imageServerURL;
}