Q: Unable to send pictures through text after update 9.2.1

Is MMS messaging enabled in Settings/Messages?

Did you already try to force restart the phone by holding the sleep and home button for about 10sec, until the Apple logo comes back? You will not lose data by doing that, but it can cure some glitches.

Can you send pictures, using iMessage?

Did you check for carrier settings update? MMS service is provided by the carrier.

Hi Samantha,

Try plugging into iTunes and then hols the sleep and hold button until the Apple logo appears.

Hope this helps,

Aaron

No it won't, that only happens if you put it in DFU mode which is done in another way. If you need instructions, please don't hesitate to ask!

Aaron

When you see the option to Restore or Update, choose Update. iTunes will try to reinstall iOS without erasing your data. Wait while iTunes downloads the software for your device.
If the download takes more than 15 minutes and your device exits recovery mode, you'll need to repeat these steps and choose Restore instead of Update when you get back to this step.

copied from: If you can't update or restore your iPhone, iPad, or iPod touch - Apple Support

+1.  I called MetroPCS. Definitely an iOs 9.2.1 problem.  Seems like 9.2.1 is not playing well with MetroPCS' unchanged version of APN settings (23.1).  MetroPCS had me "reset network settings" but that didn't fix the problem.  It looks like either Apple needs to fix iOs 9.2.1 or MetroPCS (and T-Mobile) need to update their APN settings to play with iOs 9.2.1.

Since MetroPCS is now a T-Mobile company, the same carrier settings conflict problem will likely present for T-Mobile customers too.

Installing the T-Mobile APN settings from unlockit.co.nz fixed it temporarily but the problem came back.