If I change the Theme, for example on Twenty Seventeen, this works flawlessly.
I use Corporate Plus Pro without changing any other setting, it does not work.

— Site Info —

Site URL: https://seitensprung.de
Home URL: https://seitensprung.de
Multisite: No

— Hosting Provider —

Host: DBH: localhost, SRV: seitensprung.de

— WordPress Configurations —

Version: 4.8-RC2-40868
Language: de_DE
Permalink Structure: /%category%/%year%/%monthnum%/%day%/%postname%/
Active Theme: Corporate Plus Pro Child 1.0.0
Page On Front: seitensprung.de, oder was machst Du heute Abend? Das neue Portal für den gepflegten Seitensprung! (#66384)
Page For Posts: Aktuelle News rund um seitensprung.de (#165)
All Posts/Pages: 48
WP Remote Post: wp_remote_post() works
WP_DEBUG: Enabled
WP Table Prefix: Length: 3, Status: Acceptable
Memory Limit: 512MB

— UM Configurations —

Version: 1.3.84
Upgraded From: None
Current URL Method: SERVER_NAME
Cache User Profile: Yes
Generate Slugs on Directories: Yes
Rewrite Rules: Yes
Force UTF-8 Encoding: No
Time Check Security: Yes
JS/CSS Compression: Yes
Nav Menu Settings: Yes
Port Forwarding in URL: No
Exclude CSS/JS on Home: No

— UM Total Users —

All Users(56537)
administrator(5)
editor(2)
subscriber(24036)
customer(32520)
bbp_participant(5)
none(0)

— Web Server Configurations —

PHP Version: 7.1.5
MySQL Version: 5.7.16
Web Server Info: Apache

— PHP Configurations —

PHP Memory Limit: 512M
PHP Upload Max Size: 32M
PHP Post Max Size: 32M
PHP Upload Max Filesize: 32M
PHP Time Limit: 240
PHP Max Input Vars: 2000
PHP Arg Separator: &
PHP Allow URL File Open: No

— Web Server Extensions/Modules —

DISPLAY ERRORS: On (1)
FSOCKOPEN: Your server supports fsockopen.
cURL: Your server supports cURL.
cURL-Version: 7.38.0, OpenSSL/1.0.1t
SOAP Client: Your server has the SOAP Client enabled.
SUHOSIN: Your server does not have SUHOSIN installed.
GD Library: PHP GD library is installed on your web server.
Mail: PHP mail function exist on your web server.

— Session Configurations —

Session: Enabled
Session Name: PHPSESSID
Cookie Path: /
Save Path: /tmp
Use Cookies: On
Use Only Cookies: On

— WordPress Active Plugins —

Redux Framework von Team Redux – 3.6.5
Ultimate Addons for Visual Composer von Brainstorm Force – 3.16.9
Acme Demo Setup von Acme Themes – 1.0.4
Affiliate Links Lite von TeamDev Ltd – 2.2
iThemes Security von iThemes – 6.2.1
Contact Form 7 von Takayuki Miyoshi – 4.8
EU Cookie Law von Alex Moss, Marco Milesi, Peadig, Shane Jones – 2.10
GET Params von Dan Lester – 1.1
Google Captcha (reCAPTCHA) by BestWebSoft von BestWebSoft – 1.30
Jetpack von WordPress.com von Automattic – 4.9
WPBakery Visual Composer von Michael M – WPBakery.com – 5.1
Loco Translate von Tim Whitlock – 2.0.14
McAfee SECURE von McAfeeSECURE – 1.7.5
myCRED von Gabriel S Merovingi – 1.7.8.1
Slider Revolution von ThemePunch – 5.4.1
Datenbank bereinigen und optimieren von CAGE Web Design | Rolf van Gelder, Eindhoven, Niederlande – 4.2.2
Shariff Wrapper von Jan-Peter Lambeck & 3UU – 4.3.0
Templatera von WPBakery – 1.1.11
Ultimate Member von Ultimate Member – 1.3.84
Ultimate Member – Social Activity von Ultimate Member – 1.3.3
Ultimate Member – Instagram von Ultimate Member – 1.0.2
Ultimate Member – MailChimp von Ultimate Member – 1.1.8
Ultimate Member – Private Nachrichten von Ultimate Member – 1.1.2
Ultimate Member – myCRED von Ultimate Member – 1.2.2
Ultimate Member – Real-time Notifications von Ultimate Member – 1.4.2
Ultimate Member – Online Users von Ultimate Member – 1.1.0
Ultimate Member – Profile Completeness von Ultimate Member – 1.2.0
Ultimate Member – User Reviews von Ultimate Member – 1.2.2
Ultimate Member – Social Login von Ultimate Member – 1.4.6
Ultimate Member – User Tags von Ultimate Member – 1.0.2
Ultimate Member – Verified Users von Ultimate Member – 1.0.8
Ultimate Member – WooCommerce von Ultimate Member – 1.0.11
Widget Importer & Exporter von churchthemes.com – 1.4.5
WooCommerce Stripe Gateway von WooCommerce – 3.1.9
WooCommerce Germanized von Vendidero – 1.8.11
WooCommerce von Automattic – 3.0.7
WordPress Importer von wordpressdotorg – 0.6.3
WP Maintenance Mode von Designmodo – 2.0.9
Forums – wpForo von gVectors Team (A. Chakhoyan, R. Hovhannisyan) – 1.3.0

— Theme —
Name: Corporate Plus Pro Child
Version: 1.0.0
URL des Autors: http://www.acmethemes.com/
Child Theme: On
Eltern-Theme Name: Corporate Plus Pro
Eltern-Theme Version: 1.3.1
Eltern-Theme Entwickler-URL: http://www.acmethemes.com/
Unterstützung für WooCommerce: Yes

### End System Info ###

Hallo Support,

i have make:

1) Desinstall Corporate Plus Test
2) Desinstall Corporate Plus Pro
3) Install Corporate Plus Pro

and the same :-[

Sorry

Regards Detlev