As far as I can tell the FTP server seems to be running in some sort of stealth mode if you will. So if you login in with some sort of GUI ftp client there is no directory listing.
If you know the files path and name you might still be able to get to the file.
I was able to use wget with a few command line switches to set the ftp username to anoymous with a ftp password as my email address to download a few files.
I was also able to use the a command line ftp program to login then cd to the path I needed and then issue the get command to pull down the file.
Clearly not as easy as it once was. My guess the website was never updated to reflect that that most browsers no longer have
ftp:// as a protocol option.
Anyways good luck getting any files you need.
... The seminar on time travel will be held two weeks ago
--- Mystic BBS v1.12 A47 2021/12/24 (Linux/64)
* Origin: RVs and RPGs BBS