my 4g won't turn on

[cruise350]

A few things could be going on here. The area of LA your in may not have coverage yet. Does it say scanning or turning on? 4g doesn't work on the custom rom your using. Or you used clockwork mod recovery to do your nandroid back up and your rsa keys didn't get backed up and when you restored you nandroid back up your rsa keys were lost permanently breaking your 4g on your phone. Hopefully it is one of the first 2, because if your rsa keys are gone there is no fix except replacing the phone. Read up on it over at xda. And switch your recovery to Aman Ra to do a full nandroid backup before its to late.