If you get Your Facebook account has not been verified message upon connecting your Facebook account to GI Center profile, you should first confirm your mobile phone number. Try following these steps:
1) Make sure that you entered the correct mobile number while registrating your Facebook profile.
2) Try resending the SMS with the code.
3) You can also try creating a Facebook account with your email instead of a mobile number.
You can find more information and the source article here.
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