Unity can't find the image that you've written at "TargerPath".
If you're using the type option "StreamingAssets" just write the image's name e.g. "Image.png".
If you're using the "Absote" option you may paste the same url in Windows Explorer (I don't know if Finder has the same option) to check if the url is working properly.
Also, you may change the "ImageTargetBehaviour" to use a Sprite or UnityWebRequest instead of WWW.