Q & A

Make sure the server type is standalone
ServerType Standalone

Next load the module in the proftpd.conf

<IfModule mod_cap.c>
CapabilitiesEngine on
CapabilitiesSet +CAP_CHOWN
</IfModule>
Set the directory permissions for the right user/homedir, make sure this path is the same as the DefaultRoot
<Directory /var/www>
UserOwner apache
GroupOwner apache
Umask 002 003
</Directory>
It could be that the user needs rights to the apache group.
adduser ftpusername
usermod -g apache ftpusername