Connection to storage server failed

Roundcube ‘connection to storage server failed’ error in ubuntu first-time vestacp installation
vi /etc/exim4/exim4.conf.template
#CLAMD = yes
vi /etc/clamav/clamd.conf
# AllowSupplementaryGroups yes
vi /etc/dovecot/dovecot.conf
protocols = imap pop3
listen = *
base_dir = /var/run/dovecot/
!include conf.d/*.conf
namespace inbox {
inbox = yes
}
service dovecot restart
change database configurations
vi /etc/roundcube/debian-db.php