No Files after upgrading to NC 16.0.9.2

Nextcloud version: 16.0.9.2
Operating system and version: Ubuntu 18.04.4
Apache or nginx version : Apache/2.4.29
PHP version: PHP 7.2.24-0ubuntu0.18.04.3

The issue you are facing:

No files are visible in the browser after an upgrade from 15.0.14 to 16.0.9.2 running sudo -u www-data php updater.phar (a sudo -u www-data php occ upgrade was done after the upgrade)
The upgrade seems seems to have run fine (Upgrade NC15 -> NC16 failed) - no errors it seems.

Is this the first time you’ve seen this error?: Y

Steps to replicate it:

not sure if this is replicable, an upgrade from a vanilla 15.0.14 installation to 16.x works fine and all files are visible. only the production-system facing this problem.

The output of your Nextcloud log in Admin > Logging:

I did this upgrade 2 weeks ago - sorry i don't have that output.

The output of your config.php:

<?php
$CONFIG = array (
  'passwordsalt' => '',
  'secret' => '',
  'trusted_domains' =>
  array (
    0 => 'localhost',
    1 => '',
    2 => '',
    3 => '',
    4 => '',
  ),
  'datadirectory' => '/var/www/data',
  'overwrite.cli.url' => 'http://localhost',
  'dbtype' => 'mysql',
  'version' => '16.0.9.2',
  'dbname' => '',
  'dbhost' => 'localhost',
  'dbport' => '',
  'dbtableprefix' => '',
  'mysql.utf8mb4' => true,
  'dbuser' => '',
  'dbpassword' => '',
  'installed' => true,
  'instanceid' => '',
  'maintenance' => true,
  'theme' => '',
  'loglevel' => 2,
  'memcache.local' => '\\OC\\Memcache\\APCu',
  'mail_from_address' => '',
  'mail_smtpmode' => 'smtp',
  'mail_sendmailmode' => 'smtp',
  'mail_smtphost' => '',
  'data-fingerprint' => '',
  'mail_smtpsecure' => 'tls',
  'mail_smtpauthtype' => 'LOGIN',
  'mail_smtpauth' => 1,
  'mail_smtpport' => '587',
  'mail_smtpname' => '',
  'mail_smtppassword' => '',
  'mail_domain' => '',
  'twofactor_enforced' => 'false',
  'twofactor_enforced_groups' =>
  array (
  ),
  'twofactor_enforced_excluded_groups' =>
  array (
  ),
);

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

I ran the upgrade 2 weeks ago on a production system and therefore can not provide current log-files.

how would i find out what is going wrong?
what should i do after i run the upgrade to find out how to fix this?

thanks for any help.

My notes on upgrading from NC15 to NC16 indicate that I could not login after the update.

I ran this command, which allowed me to login again:

occ maintenance:repair

Once I could login, I navigated to /settings/admin/overview, where I saw a message saying I needed to run this command (so I did):

occ db:add-missing-indices

Thank you for your tip!

After all it was not an issue with nextcloud but turned out to be a problem with cloudflare.
disabling caching on the domain “fixed” the problem.

in retrospect, upgrading nextcloud was very smooth.