Occ command broken / cannot access database?

using occ after upgrade vom 19.6 to 20.0.4 is no longer possible.

root:/var/www/html# sudo -u www-data php /var/www/html/occ -h
An unhandled exception has been thrown:
Doctrine\DBAL\DBALException: Failed to connect to the database: An exception occurred in driver: SQLSTATE[HY000] [1045] Access denied for user 'ncdata'@'localhost' (using password: NO) in /var/www/html/lib/private/DB/Connection.php:72

Nextcloud version (eg, 18.0.2): 20.0.4
Operating system and version (eg, Ubuntu 20.04): Ubuntu 16.04.7 LTS
Apache or nginx version (eg, Apache 2.4.25): Apache/2.4.18 (Ubuntu)
PHP version (eg, 7.1): PHP 7.3.25-1+ubuntu16.04.1

Is this the first time you’ve seen this error? (Y/N): Y

The output of your Nextcloud log in Admin > Logging:

no output

The output of your config.php file in /path/to/nextcloud (make sure you remove any identifiable information!):

$CONFIG = array (
  'instanceid' => 'xxx',
  'passwordsalt' => 'xxx',
  'secret' => 'xxx',
  'trusted_domains' =>
  array (
    0 => 'host.domain.de',
    1 => 'host2.domain.de',
  ),
  'datadirectory' => '/var/data',
  'dbtype' => 'mysql',
  'version' => '20.0.4.0',
  'overwrite.cli.url' => 'http://host.domain.de',
  'dbname' => 'ncdata',
  'dbhost' => 'localhost:3306',
  'dbport' => '',
  'dbtableprefix' => 'oc_',
  'dbuser' => 'ncdata',
  'installed' => true,
  'memcache.local' => '\\OC\\Memcache\\APCu',
  'mail_smtpmode' => 'sendmail',
  'mail_sendmailmode' => 'smtp',
  'mail_from_address' => 'cloud',
  'mail_domain' => 'domain.de',
  'mail_smtpauthtype' => 'PLAIN',
  'mail_smtphost' => 'smtp.web.de',
  'mail_smtpport' => '587',
  'mail_smtpsecure' => 'ssl',
  'mail_smtpauth' => 1,
  'mail_smtpname' => 'xxx@web.de',
  'mail_smtppassword' => 'xxx',
  'maintenance' => false,
  'mysql.utf8mb4' => false,
  'theme' => '',
  'app.mail.transport' => 'php-mail',
  'debug' => false,
  'loglevel' => 3,
  'updater.release.channel' => 'stable',
  'app_install_overwrite' =>
  array (
    0 => 'registration',
  ),
  'updater.secret' => 'xxx',
  'encryption.legacy_format_support' => true,
  'encryption.key_storage_migrated' => false,
);

The output of your Apache/nginx/system log in /var/log/____:

no output