iOS App showing End-to-End Encryption Not Available

Nextcloud version: 2TB Nextcloud HanssonIT VM 23.0.1
Operating system and version: Ubuntu 20.04.3 LTS (Focal Fossa)
Apache or nginx version: Apache 2.4.41
PHP version: 7.4

The issue you are facing:
iOS App showing End-to-End Encryption Not Available

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

Steps to replicate it:
1. Enabled Under Settings > Security > Server-side encryption
2. Enable App > Default Encryption Module
3. Open iOS App > Settings > End-to-End Encryption > See error

The output of your Nextcloud log in Admin > Logging:
https://pastebin.com/HhJr2tjP

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

<?php
$CONFIG = array (
  'passwordsalt' => 'RADICATED',
  'secret' => 'RADICATED',
  'trusted_domains' =>
  array (
    0 => 'localhost',
    1 => '192.168.0.RADICATED',
    2 => 'cloud.RADICATED.co.uk',
    3 => 'cloud.RADICATED.co.uk',
  ),
  'datadirectory' => '/mnt/ncdata',
  'dbtype' => 'pgsql',
  'version' => '23.0.1.2',
  'overwrite.cli.url' => 'https://cloud.RADICATED.co.uk/',
  'dbname' => 'nextcloud_db',
  'dbhost' => 'localhost',
  'dbport' => '',
  'dbtableprefix' => 'oc_',
  'dbuser' => 'RADICATED',
  'dbpassword' => 'RADICATED',
  'installed' => true,
  'instanceid' => 'ocb25fqgsdvi',
  'upgrade.disable-web' => true,
  'log_type' => 'file',
  'logfile' => '/var/log/nextcloud/nextcloud.log',
  'loglevel' => '2',
  'log.condition' =>
  array (
    'apps' =>
    array (
      0 => 'admin_audit',
    ),
  ),
  'mail_smtpmode' => 'smtp',
  'remember_login_cookie_lifetime' => '7200',
  'log_rotate_size' => '0',
  'trashbin_retention_obligation' => 'auto, 60',
  'versions_retention_obligation' => 'auto, 180',
  'activity_expire_days' => '120',
  'simpleSignUpLink.shown' => false,
  'memcache.local' => '\\OC\\Memcache\\Redis',
  'filelocking.enabled' => true,
  'memcache.distributed' => '\\OC\\Memcache\\Redis',
  'memcache.locking' => '\\OC\\Memcache\\Redis',
  'redis' =>
  array (
    'host' => '/var/run/redis/redis-server.sock',
    'port' => 0,
    'timeout' => 0.5,
    'dbindex' => 0,
    'password' => 'RADICATED',
  ),
  'default_phone_region' => 'gb',
  'logtimezone' => 'Europe/London',
  'htaccess.RewriteBase' => '/',
  'session_lifetime' => '7200',
  'enable_previews' => true,
  'preview_max_x' => '2048',
  'preview_max_y' => '2048',
  'jpeg_quality' => '60',
  'trusted_proxies' =>
  array (
    0 => '127.0.0.1',
  ),
  'ldapProviderFactory' => 'OCA\\User_LDAP\\LDAPProviderFactory',
  'maintenance' => false,
  'enabledPreviewProviders' =>
  array (
    0 => 'OC\\Preview\\PNG',
    1 => 'OC\\Preview\\JPEG',
    2 => 'OC\\Preview\\GIF',
    3 => 'OC\\Preview\\BMP',
    4 => 'OC\\Preview\\MarkDown',
    5 => 'OC\\Preview\\MP3',
    6 => 'OC\\Preview\\TXT',
    7 => 'OC\\Preview\\Movie',
    8 => 'OC\\Preview\\Photoshop',
    9 => 'OC\\Preview\\SVG',
    10 => 'OC\\Preview\\TIFF',
  ),
  'app_install_overwrite' =>
  array (
    0 => 'integration_whiteboard',
    1 => 'pdfannotate',
  ),
  'twofactor_enforced' => 'true',
  'twofactor_enforced_groups' =>
  array (
    0 => 'admin',
    1 => 'Users',
  ),
  'twofactor_enforced_excluded_groups' =>
  array (
  ),
  'updater.release.channel' => 'beta',
  'mail_smtpsecure' => 'ssl',
  'mail_sendmailmode' => 'smtp',
  'mail_from_address' => 'contact',
  'mail_domain' => 'RADICATED.co.uk',
  'mail_smtpauthtype' => 'LOGIN',
  'mail_smtpauth' => 1,
  'mail_smtphost' => 'smtp.RADICATED.com',
  'mail_smtpport' => '465',
  'mail_smtpname' => 'contact@RADICATED.co.uk',
  'mail_smtppassword' => 'RADICATED',
);

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

Not sure - Linux n00b :-/

Resolved the issue
Went to Apps
Featured Apps
Clicked Download and Enable “End-to-End Encryption”

Different to the documented " Default Encryption Module"