Problem with license key

At my job, we’ve bought the AAM Plus Package for our website. I know how to register with

[aam] license_key = “my license key”

with the key I’ve received but it does not work and my AAM Plus Package is still locked. When I create a new user category and click on the little gear on my user list and try to assign a specific post and page to that user, I don’t have all the options (red lock telling me to register).

WordPress version: 3.8.1
Plugin version: 2.3 (downloaded through the WordPress extension)

Do we have to add something else?
Thanks a lot

https://wordpress.org/plugins/advanced-access-manager/