phpMyAdmin is not working: session_start(): Failed to read session data: files (path: ./tmp/session)

Applicable to:

The following error message occurs on an attempt to open phpMyAdmin in Domains > example.com > Databases or in Tools & Settings > Database Servers > next to the MySQL server name:

CONFIG_TEXT: Error during session start; please check your PHP and/or webserver log file and configure your PHP installation properly. Also ensure that cookies are enabled in your browser.

session_start(): open(SESSION_FILE, O_RDWR) failed: No such file or directory (2)
session_start(): Failed to read session data: files (path: ./tmp/session)
SessionSavePath is set to ./tmp/session:

Debian, Ubuntu:

# grep -rin 'SessionSavePath' /opt/psa/admin/htdocs/domains/databases/phpMyAdmin/libraries/config.default.php
716:$cfg['SessionSavePath'] = './tmp/session';

CentOS:

# grep -rin 'SessionSavePath' /usr/local/psa/admin/htdocs/domains/databases/phpMyAdmin/libraries/config.default.php
716:$cfg['SessionSavePath'] = './tmp/session';
phpMyAdmin package is not configured:

# dpkg -l | grep -i phpmyadmin
iU psa-phpmyadmin 4.8.3-ubuntu16.04.build1708180919.15 all MySQL web administration tool adapted for Plesk Onyx

The package psa-phpmyadmin is not configured.

The proper SessionSavePath should be /opt/psa/var/phpMyAdmin/session for Debian/Ubuntu or /usr/local/psa/var/phpMyAdmin/session for CentOS.

Debian, Ubuntu:

Connect to the server using SSH.
Configure psa-phpmyadmin package:

# dpkg-reconfigure psa-phpmyadmin
Verify that the path is proper now:

# grep SessionSavePath /opt/psa/admin/htdocs/domains/databases/phpMyAdmin/libraries/config.default.php
$cfg['SessionSavePath'] = '/opt/psa/var/phpMyAdmin/session';

CentOS:

Connect to the server using SSH;
Go to http://autoinstall.plesk.com and download package with the PHPMyAdmin of the required version in PSA<Plesk panel version> > dist-rpm<OS version> > psa-phpmyadmin<> package (example for psa-phpmyadmin-4.8.3-cos7.build1708180919.15.noarch.rpm):

# wget http://autoinstall.plesk.com/PSA_17.8.11/dist-rpm-CentOS-7-x86_64/base/psa-phpmyadmin-4.8.3-cos7.build1708180919.15.noarch.rpm
Reinstall the psa-phpmyadmin package:

# rpm -Uvh psa-phpmyadmin-4.8.3-cos7.build1708180919.15.noarch.rpm --force
Verify that the path is proper now:

# grep 'SessionSavePath' /usr/local/psa/admin/htdocs/domains/databases/phpMyAdmin/libraries/config.default.php
$cfg['SessionSavePath'] = '/usr/local/psa/var/phpMyAdmin/session';