Can you make/receive calls normally? If not, then you may have been suspended and will take a little bit of time to get reconnected.
If so, then toggle the radio connection under your Manage Connections icon. Toggle that a couple of times. Give it 30 seconds to 1 minute to pick up the EV signal. Still not working? Pull the battery a couple of times. Still not working? Try *228 and option 1 then toggle the radio connection again.
Still not working? Sheesh. Try resending your service books. Click on email settings, log in and hit your menu button then select service books and resend.
Still not working? A. There may be an issue in your area. B. Your device may be defective. C. You're doin it wrong.