For security reasons, the "postgres" login is not allowed to access the database via "phppgadmin". To allow it, you need to modify the file /etc/phppgadmin/config.inc.php. In this file, set "false" on the following line:
$conf['servers'][1]['desc'] = 'Server2'; // Don't forget to change the number (1) to indicate the server, then the server name to display$conf['servers'][1]['host'] = '192.168.0.87'; // The IP of the server$conf['servers'][1]['port'] = 5432;$conf['servers'][1]['sslmode'] = 'allow';$conf['servers'][1]['defaultdb'] = 'template1';$conf['servers'][1]['pg_dump_path'] = '/usr/bin/pg_dump';$conf['servers'][1]['pg_dumpall_path'] = '/usr/bin/pg_dumpall';$conf['servers'][1]['slony_support'] = false;$conf['servers'][1]['slony_sql'] = '/usr/share/postgresql';$conf['servers'][2]['desc'] = 'Server3';$conf['servers'][2]['host'] = '192.168.0.89';$conf['servers'][2]['port'] = 5432;$conf['servers'][2]['sslmode'] = 'allow';$conf['servers'][2]['defaultdb'] = 'template1';$conf['servers'][2]['pg_dump_path'] = '/usr/bin/pg_dump';$conf['servers'][2]['pg_dumpall_path'] = '/usr/bin/pg_dumpall';$conf['servers'][2]['slony_support'] = false;$conf['servers'][2]['slony_sql'] = '/usr/share/postgresql';