Unable to display mms image or video
If you try to view mms images or videos using another app (ie. Gallery, Google+ Pictures) but you get a blank (or grey) screen instead, you may be suffering from a permissions problem.
In order for an app to display an image or video (or some other media) from an mms message, it needs to have the permission "READ SMS". Please check that the app you are using has this permission.
Alternatively, test by viewing the image or video using the default app (usually Gallery) on your device. The default app usually has the required permission.
However, there have been situations where some users have removed the "READ SMS" permission from the default app (using "App Ops") and then are unable to view mms images or video with it.