Ppure-ftpd virtual users does not work

Hello, I’m installing Ppure-ftpd 1.0.49 and in the default config file the line with virtual users is completely commented out. I have been using pure-ftpd for many years, but this is the first time I have met this.

# PureDB user database (see README.Virtual-Users)
# PureDB                       @sysconfigdir@/pureftpd.pdb

If I uncomment, I get that the program cannot read pureftpd.pdb and it is not clear how to solve this problem. Regular PAM authentication works fine out of the box. I tried to copy pureftpd.pdb to the /usr/etc and /usr/local/etc but no result. Tell me how you can enable virtual users?