Did you enter a date of birth when creating your Adobe account? If you are under 18 you wont be able to access. If you are over, go to https://www.behance.net/ and set up a profile choose the correct DOB, after which you should be able to access AI fetures.
In case you can't adjust or add your DOB, you would have to contact a support https://helpx.adobe.com/support.html so they can alter the changes
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