I don't see the Image Measurement Widget in the app that you have linked. Do you have an Image service in your app that has the mensuration capability?
The Image Measurement widget allows you to perform measurements on image services with mensuration capability. Mensuration is a method of applying geometric rules to find length of lines, area of surfaces, or volume using information obtained from lines and angles. It can also include measuring the height and absolute location of a feature.
I am sorry for the trouble but I removed the widget in order to take some screenshots. It is back in now if you can check it. The layer that has mensuration capability is the ForestFire (preliminary assessment) one.
Also, I have a problem with GeoLookUp Widget. It says that it has enriched the csv points with info from all layers (ForestFire, Slope, Aspect, Corine 2012), but it only uses ForestFire and Corine 2012. Any ideas?