Why is Siri greyed out on my text message keyboard and how do I turn it back on?
Settings>General>Siri>On or check Settings>General>Restrictions>Siri>On
Make sure you have an active data connection (either 3G or WiFi).
I resolved the issue FYI Siri was on and operating in all applications except text messaging the solution was to do a hard restart holding home button while shutting down
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