Why can proFtpd return 530 error (Login incorrect)?

Question

System administration

Installed ptoFtpd according to the manual from the Internet.
Added in config

UseIPv6 off
IdentLookups off
PassivePorts 40900 40999
RequireValidShell off
AuthUserFile /etc/proftpd.d/ftpd.passwd
AuthPAM off
LoadModule mod_auth_file.c
AuthOrder mod_auth_file.c

Created a user with the command

ftpasswd --passwd --file=/etc/proftpd.d/ftpd.passwd --name=ftpwww --uid=48 --gid=48 --home=/var/www --shell=/sbin/nologin

when trying to connect, a
530 Login incorrect response is returned.
Why can this happen?