If the access for administrator from address '127.0.0.1' is restricted by the administrator, all interactions between the Parallels Plesk Panel and Customer & Business Manager (including the initial configuration) are not possible.
# cat /etc/hosts
# Do not remove the following line, or various programs
# that require network functionality will fail.
::1 localhost6.localdomain6 localhost6
#127.0.0.1 localhost.localdomain localhost <-----this one is to be commented
<IP_address> <hostname> localhost.localdomain localhost <-----this one is to be added