Unable to see federated shared files

Nextcloud version (eg, 20.0.5): 28.0.1
Operating system and version (eg, Ubuntu 20.04): docker/AIO
Apache or nginx version (eg, Apache 2.4.25): docker/AIO
PHP version (eg, 7.4): docker/AIO

The issue you are facing:
I am unable to access files shared between 2 NC-AIO servers via federation. I have 2 Nextcloud-AIO servers. This fails in both directions.

Server 1 is using local storage.
Server 2 is using block storage.

Both sit behind an instance of Nginx Proxy Manager.
Both are using valid SSL certificates via letsencrypt.

I added the hosts to one another as trusted servers. After some searching and effort was able to get them both to turn green. [Bug]: Trusted Server Stuck at Yellow/Orange · Issue #39941 · nextcloud/server · GitHub

When I share a file I get the notification on the other server that a file was shared. I click Accept in the notification and I’ll get an alert that the share was accepted. The problem is, when look at “Shared with you” it’s empty.

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

Steps to replicate it:

  1. Share a document from user@serverA to user@serverB
  2. Accept the share
  3. Look in “Shared with you”, it’s empty.

The output of your Nextcloud log in Admin > Logging:
ServerB - Below are all the log messages for yesterday.

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

<?php
$CONFIG = array (
  'one-click-instance' => true,
  'one-click-instance.user-limit' => 100,
  'memcache.local' => '\\OC\\Memcache\\APCu',
  'apps_paths' =>
  array (
    0 =>
    array (
      'path' => '/var/www/html/apps',
      'url' => '/apps',
      'writable' => false,
    ),
    1 =>
    array (
      'path' => '/var/www/html/custom_apps',
      'url' => '/custom_apps',
      'writable' => true,
    ),
  ),
  'appsallowlist' =>
  array (
  ),
  'check_data_directory_permissions' => false,
  'memcache.distributed' => '\\OC\\Memcache\\Redis',
  'memcache.locking' => '\\OC\\Memcache\\Redis',
  'redis' =>
  array (
    'host' => 'nextcloud-aio-redis',
    'password' => 'redacted',
    'port' => 6379,
  ),
  'overwritehost' => 'host.domain.tld',
  'overwriteprotocol' => 'https',
  'passwordsalt' => 'redacted',
  'secret' => 'redacted',
  'trusted_domains' =>
  array (
    0 => 'localhost',
    1 => 'host.domain.tld',
  ),
  'datadirectory' => '/mnt/ncdata',
  'dbtype' => 'pgsql',
  'version' => '28.0.1.1',
  'overwrite.cli.url' => 'redacted',
  'dbname' => 'nextcloud_database',
  'dbhost' => 'nextcloud-aio-database',
  'dbport' => '',
  'dbtableprefix' => 'oc_',
  'dbuser' => 'oc_nextcloud',
  'dbpassword' => 'redacted',
  'installed' => true,
  'instanceid' => 'redacted',
  'maintenance' => false,
  'updatedirectory' => '/nc-updater',
  'loglevel' => '2',
  'app_install_overwrite' =>
  array (
    0 => 'nextcloud-aio',
    1 => 'unsplash',
  ),
  'log_type' => 'file',
  'logfile' => '/var/www/html/data/nextcloud.log',
  'log_rotate_size' => '10485760',
  'log.condition' =>
  array (
    'apps' =>
    array (
      0 => 'admin_audit',
    ),
  ),
  'preview_max_x' => '2048',
  'preview_max_y' => '2048',
  'jpeg_quality' => '60',
  'enabledPreviewProviders' =>
  array (
    1 => 'OC\\Preview\\Image',
    2 => 'OC\\Preview\\MarkDown',
    3 => 'OC\\Preview\\MP3',
    4 => 'OC\\Preview\\TXT',
    5 => 'OC\\Preview\\OpenDocument',
    6 => 'OC\\Preview\\Movie',
    7 => 'OC\\Preview\\Krita',
    0 => 'OC\\Preview\\Imaginary',
  ),
  'enable_previews' => true,
  'upgrade.disable-web' => true,
  'mail_smtpmode' => 'smtp',
  'trashbin_retention_obligation' => 'auto, 30',
  'versions_retention_obligation' => 'auto, 30',
  'activity_expire_days' => '30',
  'simpleSignUpLink.shown' => false,
  'share_folder' => '/Shared',
  'one-click-instance.link' => 'https://nextcloud.com/all-in-one/',
  'upgrade.cli-upgrade-link' => 'https://github.com/nextcloud/all-in-one/discussions/2726',
  'allow_local_remote_servers' => true,
  'davstorage.request_timeout' => 3600,
  'htaccess.RewriteBase' => '/',
  'dbpersistent' => false,
  'files_external_allow_create_new_local' => false,
  'trusted_proxies' =>
  array (
    0 => '127.0.0.1',
    1 => '::1',
    2 => 'proxy_ip',
  ),
  'preview_imaginary_url' => 'http://nextcloud-aio-imaginary:9000',
  'objectstore' =>
  array (
    'class' => 'OC\\Files\\ObjectStore\\S3',
    'arguments' =>
    array (
      'bucket' => 'bucket',
      'autocreate' => true,
      'key' => 'key',
      'secret' => 'secret',
      'hostname' => 'hostname',
      'port' => 443,
      'use_ssl' => true,
      'region' => 'region',
      'use_path_style' => false,
    ),
  ),
  'filelocking.enabled' => false,
  'mail_domain' => 'domain',
  'mail_from_address' => 'user',
  'mail_smtphost' => 'host',
  'mail_sendmailmode' => 'smtp',
  'mail_smtpport' => '25',
  'default_phone_region' => 'US',
  'twofactor_enforced' => 'true',
  'twofactor_enforced_groups' =>
  array (
  ),
  'twofactor_enforced_excluded_groups' =>
  array (
  ),
  'defaultapp' => '',
);

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

I’m not clear which logs to send on AIO.

Output errors in nextcloud.log in /var/www/ or as admin user in top right menu, filtering for errors. Use a pastebin service if necessary.

See above pastebin.