Maxmind changed their download mechanism again, this time with very little warning. cvmfs_server add-replica on new servers is now broken, as well as geodb updates.
The details are on their blog. Effective the end of 2019, in order to download their free databases you have to create an account on their website and get a license key. The URL for downloading has also changed.
This is unfortunately quite an onerous requirement but they say they have to do it in order to comply with privacy laws and I think we'll just have to adapt. I will make a pull request and we'll need a new cvmfs release soon.