I am guessing you are not in a 4G coverage area, have you tried switching the device to use 3G only with https://play.google.com/store/apps/details?id=net.andirc.lteonfoff&feature=search_result#?t=W251bGwsMSwxLDEsIm5ldC5hbmRpcmMubHRlb25mb2ZmIl0. and see if this helps?
Mine was having these problems until I called Verizon and they had to send a reactivate/refresh on my Si
It's sure aggravating when you want to send an important picture and it doesn't go through. I understand this and am prepared to assist you!
To troubleshoot, please first complete a soft reset on the phone. Don't worry, you will not lose any data. Here is a link for that http://bit.ly/w7N1Ik . Next, please send a picture to your own mobile number to check both the incoming and outgoing capabilities of the device.
If you are still having issues after completing these steps, feel free to send me a DM and I will be more than happy to assist you further.
Thanks for bringing this to our attention!
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