Recently, some companies have changed their policy regarding support for FTP URLs. Already, FTP is no longer enabled by default in latest versions of web browsers such as Firefox and Chrome (to name a few) but can be set manually (see below).
As FTP support will be removed completely from most web browsers in future releases, users are encouraged to consider other options such as the secure shell file transfer protocol (SFTP), or a third-party application like FileZilla (free - compatible with Windows, Mac and Linux) to download the BigBrain data.
More info and some tips:
deprecate FTP support (deprecated) in Chrome
enable FTP in Chrome
enable FTP in Firefox