IPhone 5 MMS messaging doesn't work?

I'm trying to send my friend this funny picture of what I said to Siri on my iPhone 5, and it will not send. I'm on StraightTalk $45 a month, and it does include MMS. I've tried disconnecting from Wi-Fi, etc. And YES my MMS settings are turned on. Please help!
It says TFW 3G at the top, and last night, it worked fine. I got the phone yesterday evening.

Added (1). I've tried Hard Reset and turning airplane mode on and off.

Added (2). It says TFW 3G at the top, and last night, the MMS worked fine when I sent a snapshot of something to my dad. I got the phone yesterday evening.

Here is a simple way to see if you can use MMS on straight talk with an iPhone.
Go to Settings---> General--->Network
Now if you see a setting for Cellular Data, not the slider but an actual new window, where you can put in APN, MMS you can edit those for straight talk.

If not, which will be the most likely case, than you will not be able to use MMS on an iPhone for straight talk. You can thank Apple for not allowing their users the ability to edit these very simple settings that any Android will let you edit. Go Android and use what you pay for.