My Android (4.1) phone is often not receiving MMS messages in the Messaging app. It stays stuck on the "downloading" message. I have data turned on, so that's not the issue. I was also not roaming at the time. Sometimes Android would download the MMS messages, other times it would just remain on the MMS notification 'download'.
This workaround seemed to have success with my own device after several days of attempting other solutions (turning on/off background data, turning on/off wifi while 3G is turned on, etc.) Your mileage may vary, but hopefully it at least helps someone out there :)
- in the Messaging app, go to the settings
- scroll down to the "MULTIMEDIA (MMS) MESSAGES" section
- uncheck "auto-retrieve"
- when someone sends a MMS, click the "download" button that appears in place of the 'downloading ...' message
- your message should now download, rather than forever remain on the "downloading..." message
This was tested to work using Android 4.1.1 on a Samsung Galaxy Nexus while on the Fido network in Canada. Again, as many things can contribute to MMS messages not sending, your mileage may vary.
While this is not the ideal solution, most people will usually not be looking at a MMS message until they have the messaging app open in front of them, so hopefully this is an appropriate workaround for those who don't mind waiting a few seconds to manually download a MMS rather than have them automatically download.
By the way, if anyone at Google is reading this, hopefully this bug can be reproduced by your Android Messaging app team =) It's an intermittent bug and I have no idea how to reliably reproduce it, otherwise a bug report would have been filed by now! Have a great day!