MediaWiki connector basic authentication results in "Failed to verify connector credentials."

Question

I tried to do a strait forward example of using the MediaWiki connector. So started on play-with-docker.com with a MediaWiki. I used the following docker-compose.yml provided on https://hub.docker.com/_/mediawiki:

version: '3'
services:
  mediawiki:
    image: mediawiki
    restart: always
    ports:
      - 8080:80
    links:
      - database
    volumes:
      - images:/var/www/html/images
      # After initial setup, download LocalSettings.php to the same directory as
      # this yaml and uncomment the following line and use compose to restart
      # the mediawiki service
      - ./LocalSettings.php:/var/www/html/LocalSettings.php
  # This key also defines the name of the database host used during setup instead of the default "localhost"
  database:
    image: mariadb
    restart: always
    environment:
      # @see https://phabricator.wikimedia.org/source/mediawiki/browse/master/includes/DefaultSettings.php
      MYSQL_DATABASE: my_wiki
      MYSQL_USER: wikiuser
      MYSQL_PASSWORD: example
      MYSQL_RANDOM_ROOT_PASSWORD: 'yes'
    volumes:
      - db:/var/lib/mysql

volumes:
  images:
  db:

Following the setup routine resulted in the following LocalSettings.php:

<?php
# This file was automatically generated by the MediaWiki 1.42.3
# installer. If you make manual changes, please keep track in case you
# need to recreate them later.
#
# See includes/MainConfigSchema.php for all configurable settings
# and their default values, but don't forget to make changes in _this_
# file, not there.
#
# Further documentation for configuration settings may be found at:
# https://www.mediawiki.org/wiki/Manual:Configuration_settings

# Protect against web entry
if ( !defined( 'MEDIAWIKI' ) ) {
	exit;
}




## Uncomment this to disable output compression
# $wgDisableOutputCompression = true;

$wgSitename = 'Testwiki';

## The URL base path to the directory containing the wiki;
## defaults for all runtime URL paths are based off of this.
## For more information on customizing the URLs
## (like /w/index.php/Page_title to /wiki/Page_title) please see:
## https://www.mediawiki.org/wiki/Manual:Short_URL
$wgScriptPath = '';

## The protocol and server name to use in fully-qualified URLs
$wgServer = 'http://ip172-18-0-40-csiampgl2o90009joibg-8080.direct.labs.play-with-docker.com';

## The URL path to static resources (images, scripts, etc.)
$wgResourceBasePath = $wgScriptPath;

## The URL paths to the logo.  Make sure you change this from the default,
## or else you'll overwrite your logo when you upgrade!
$wgLogos = [
	'1x' => "$wgResourceBasePath/resources/assets/change-your-logo.svg",
	'icon' => "$wgResourceBasePath/resources/assets/change-your-logo.svg",
];

## UPO means: this is also a user preference option

$wgEnableEmail = true;
$wgEnableUserEmail = true; # UPO

$wgEmergencyContact = '';
$wgPasswordSender = '';

$wgEnotifUserTalk = false; # UPO
$wgEnotifWatchlist = false; # UPO
$wgEmailAuthentication = true;

## Database settings
$wgDBtype = 'mysql';
$wgDBserver = '172.19.0.2';
$wgDBname = 'my_wiki';
$wgDBuser = 'wikiuser';
$wgDBpassword = 'example';

# MySQL specific settings
$wgDBprefix = "";
$wgDBssl = false;

# MySQL table options to use during installation or update
$wgDBTableOptions = "ENGINE=InnoDB, DEFAULT CHARSET=binary";

# Shared database table
# This has no effect unless $wgSharedDB is also set.
$wgSharedTables[] = "actor";

## Shared memory settings
$wgMainCacheType = CACHE_ACCEL;
$wgMemCachedServers = [];

## To enable image uploads, make sure the 'images' directory
## is writable, then set this to true:
$wgEnableUploads = false;
$wgUseImageMagick = true;
$wgImageMagickConvertCommand = '/usr/bin/convert';

# InstantCommons allows wiki to use images from https://commons.wikimedia.org
$wgUseInstantCommons = false;

# Periodically send a pingback to https://www.mediawiki.org/ with basic data
# about this MediaWiki instance. The Wikimedia Foundation shares this data
# with MediaWiki developers to help guide future development efforts.
$wgPingback = true;

# Site language code, should be one of the list in ./includes/languages/data/Names.php
$wgLanguageCode = 'de';

# Time zone
$wgLocaltimezone = 'UTC';

## Set $wgCacheDirectory to a writable directory on the web server
## to make your wiki go slightly faster. The directory should not
## be publicly accessible from the web.
#$wgCacheDirectory = "$IP/cache";

$wgSecretKey = 'a8b0578776bd7a2ad50d73d7c99730bc01ae9bcd17703b8942da2aa098f12ad4';

# Changing this will log out all existing sessions.
$wgAuthenticationTokenVersion = '1';

# Site upgrade key. Must be set to a string (default provided) to turn on the
# web installer while LocalSettings.php is in place
$wgUpgradeKey = '88eeb7af190ca4aa';

## For attaching licensing metadata to pages, and displaying an
## appropriate copyright notice / icon. GNU Free Documentation
## License and Creative Commons licenses are supported so far.
$wgRightsPage = ""; # Set to the title of a wiki page that describes your license/copyright
$wgRightsUrl = '';
$wgRightsText = '';
$wgRightsIcon = "";

# Path to the GNU diff3 utility. Used for conflict resolution.
$wgDiff3 = '/usr/bin/diff3';

# The following permissions were set based on your choice in the installer
$wgGroupPermissions['*']['createaccount'] = false;
$wgGroupPermissions['*']['edit'] = false;
$wgGroupPermissions['*']['read'] = false;

## Default skin: you can change the default skin. Use the internal symbolic
## names, e.g. 'vector' or 'monobook':
$wgDefaultSkin = 'monobook';

# Enabled skins.
# The following skins were automatically enabled:
wfLoadSkin( 'MinervaNeue' );
wfLoadSkin( 'MonoBook' );
wfLoadSkin( 'Timeless' );
wfLoadSkin( 'Vector' );


# End of automatically generated settings.
# Add more configuration options below.

The wiki itself is working like expected.

But not the MediaWiki connector:

I tried the credentials several times. What's going wrong here? What I'm missing?

Thanks in advance.