===EDIT ===
I just reread your post, and you notice you mentioned having a no sign icon. That one is easy. it means you, or a program acting on your behalf, explicitly turned off the radios. Juice defender, LTE on/off, or another such radio control program can do that.
=== EDIT ===
This usually happens when switching from one data type to the next, like from 1x to 3g, 3g to 4g...
If yours is permanently in that state, it could be a sign that your radios are off. Are you using "juice defender" or a similar app that turns off radios?
Have you disabled data through the settings menu or restricted data switching/type through the hidden menus?
And just in case your phone's radio drivers just errored out, you could try rebooting the phone.
Also, try switching from airplane mode to normal mode and observe the status bar.
If a data icon comes and quickly disappears every time you do that, you may have fried your radios... If that's the case, your only recourse is to return it to MetroPCS for an exchange/upgrade (if it's still under warranty).