As the error message says, you need a license key.
Note: As of 2019-12-29, MaxMind REQUIRES you to create an account on their
site and to generate a license key to use their databases. See:
You MUST set the following to continue using the IP lookup features of csf,
otherwise an error will be generated and the features will not work
It changed because MaxMind changed their policy. So if you want to keep using that feature in csf you have to register and get a free license key. Per the other replies, you can read the details as to why here: