Hello. The simplest resolution is to update your data profile.
Tap Home > Apps icon > Settings.
Scroll up and tap System updates.
Tap Update Profile.
Phone will check for updates and display Attention The profile has been updated.
Tap OK to continue.
Tap Home to return to the Home screen.
If it's still failing, several things can cause this.
Your Network Access Identifier (NAI) is locked out from too many invalid attempts. This is common on Android phones since the data requests are so frequent and it only takes 10 invalid attmepts to get locked out. The lockout clears in 20 minutes if no further invalid attempts are captured by the network. Turn your phone off for 30 mintues to be sure, then retry.
There's a problem with your billing or data caused by overage. This can be checked by going to My Sprint - My Account at the top and click "See all usage" next to the picture of your phone.
Your NAI is corrupt and will need to be wiped/then reset. Customer Care can walk you through an SCRTN on the phone if you call in and request this type of reset. You will need an alternate phone to call in for this type of trouble shooting. 888.211.4727