Not sure if your problem was resolved or not, but if not, here's how I fixed the same problem. All worked fine until Android 4.4 (KitKat) was pushed. Once KitKat was pushed, the stock messaging app stopped handling attachments, sending or receiving. I switched to Hangouts instead of the stock messaging app. That worked for about a week, then that stopped. I ended up performing a factory reset, and that fixed the issue...for a week. After three factory resets, I went to the Verizon store for help. Long story short, I was sent a new phone after trying a number of software changes, removing Google+ (because there apparently is a known problem with the LG G2, KitKat, and Google+), using Verizon Messaging, and replacing the sim card. I was told not to accept the KitKat update when I got the new phone and to NOT update Google+ .
I got the new phone...and it was preloaded with KitKat. So much for not accepting that update. I ignored the Google+ updates, and MMS worked just fine...for 3 days. Remembering that the tech suggested that Google+ might be the problem, I cleared the Google+ cache, deleted the Google+ stored data, disabled the app, and restarted the phone. Since doing that, everything has been working just fine. I also realized that the Google Photo app is part of Google+, and I was using that app instead of Photos as my primary app to manage photos. That included the auto backup feature for my photos to Google+. All of this makes me suspect that the Photo app and auto backup feature may be the culprits.
