Had this issue with my 8X. The way I resolved it was to firstly check the APN settings to make sure they were correct for my provider.
Next, check to ensure the messaging centre number is correct for your provider.
Finally, force the device to register onto a different network even though you don't have an account with them and trying to connect will error. I did this with a few other networks and then connected to my correct network.
Everything should now work
Sent from my Windows 8 device using Board Express