Try power cycling your phone, Turn off remove battery for a min, Reinsert battery, reboot, Check to see if it works, If not go into the settings and update your data profile and see if it fixes it.
Have you ever been able to access the internet or did this just start? Data could be blocked on your phone/account, Go to "My Account>My Preferences>Limits & Permissions>Block Data(if there is a Green check mark your data is blocked)Uncheck it>Save.
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