Installation failed, folder already exists

Hello,

I can’t install Monster Insights, cause there is an installation fail error message ?Installation failed: The destination folder already exists“.
And it won’t be listed in …/wp-admin/plugins.php
I tried even upload per ftp, but it isn’t in the plugin list. I even deactivated all other plugins, same problem ??

Many thanks for any help.

Debugging infos from health check plugin:

### WordPress ###

Version: 5.0.3
Language: de_DE
Permalink structure: /%year%/%monthnum%/%day%/%postname%/
Is this site using HTTPS?: Yes
Can anyone register on this site?: Yes
Default comment status: open
Is this a multisite?: No
User Count: 1
Communication with www.ads-software.com: www.ads-software.com is reachable
Create loopback requests: The loopback request to your site completed successfully.

### Installation size ###

Uploads Directory: 172.54 MB
Themes Directory: 3.10 MB
Plugins Directory: 104.89 MB
Database size: 84.62 MB
Whole WordPress Directory: 894.10 MB
Total installation size: 978.72 MB

### Drop-ins ###

advanced-cache.php: Advanced caching plugin.

### Active Theme ###

Name: Twenty Ten Custom
Version: 1.2
Author: the WordPress team
Author website: Undefined
Parent theme: Not a child theme
Supported theme features: editor-style, post-formats, post-thumbnails, automatic-feed-links, menus, custom-background, custom-header, widgets

### Other themes (2) ###

Twenty Fifteen (twentyfifteen): Version 2.3 by the WordPress team
Twenty Ten (twentyten): Version 2.7 by the WordPress team

### Active Plugins (39) ###

Akismet Anti-Spam: Version 4.1.1 by Automattic
Anti-Malware Security and Brute-Force Firewall: Version 4.18.52 by Eli Scheetz
Anti-Spambot Email Shortcode: Version 1.1.3 by Robert Peake
Code Snippets: Version 2.13.2 by Shea Bunge
Disable Gutenberg: Version 1.5.2 by Jeff Starr
Duplicate Post: Version 3.2.2 by Enrico Battocchi
GigPress: Version 2.3.22 by Modern Tribe
Google+ for Page: Version 1.1 by Darko Mitrovic
Gravatar Signup: Version 2.0.1 by Mark Jaquith
Health Check & Troubleshooting: Version 1.2.5 by The www.ads-software.com community
iframe: Version 4.4 by webvitaly
Image Rotator Widget: Version 1.2.1 by Douglas Karr, Stephen Coley
Jetpack by WordPress.com: Version 7.0 by Automattic
Limit Login Attempts: Version 1.7.1 by Johan Eenfeldt
Link Footnotes: Version 0.1.7 by Ryan Nutt
MailChimp for WordPress: Version 4.3.3 by ibericode
NextGEN Gallery: Version 3.1.6 by Imagely
PHP Compatibility Checker: Version 1.4.7 by WP Engine
Pixel Cat Lite: Version 2.4.0 by Fatcat Apps
Press This: Version 1.1.1 by WordPress Contributors
Print, PDF & Email by PrintFriendly: Version 3.14.4 by Print, PDF, & Email by PrintFriendly
Really Simple SSL: Version 3.1.3 by Rogier Lankhorst, Mark Wolters
Revision Control: Version 2.3.2 by Dion Hulse
SABRE: Version 1.2.2 by Didier Lorphelin
Short URL: Version 1.6.3 by SedLex
Smush: Version 3.1.1 by WPMU DEV
Social Gallery: Version 3.8.2 by <a href = "https://about.me/michael.stott.79" target = "_blank">Mike</a>
Theme Check: Version 20190208.1 by Otto42, pross
TimThumb Vulnerability Scanner: Version 1.54 by Peter Butler
TinyMCE Advanced: Version 5.0.1 by Andrew Ozz
WordPress Database Backup: Version 2.3.3 by Austin Matzko
WP-DownloadManager: Version 1.68.4 by Lester 'GaMerZ' Chan
WP-Stats: Version 2.55 by Lester 'GaMerZ' Chan
WP BandCamp: Version 1.1.1 by LongJohn
WP Maintenance Mode: Version 2.2.2 by Designmodo
WP Super Cache: Version 1.6.4 by Automattic
WP System Health: Version 1.4.0 by Heiko Rabe
WP to Buffer: Version 3.4.5 by WP Zinc
Yoast SEO: Version 9.6 by Team Yoast

### Media handling ###

Active editor: WP_Image_Editor_Imagick
Imagick Module Version: 1673
ImageMagick Version: ImageMagick 6.8.9-9 Q16 x86_64 2018-09-28 https://www.imagemagick.org
Imagick Resource Limits: 
	area: 31 GB
	disk: -1
	file: 48750
	map: 31 GB
	memory: 16 GB
	thread: 8
GD Version: bundled (2.1.0 compatible)
Ghostscript Version: 9.26

### Server ###

Server architecture: Linux 4.4.0-142-generic x86_64
Web Server Software: Apache
PHP Version: 7.2.13-nmm1 (Supports 64bit values)
PHP SAPI: fpm-fcgi
PHP max input variables: 3000
PHP time limit: 30
PHP memory limit: 512M
Max input time: 60
Upload max filesize: 200M
PHP post max size: 200M
cURL Version: 7.47.0 OpenSSL/1.0.2g
SUHOSIN installed: No
Is the Imagick library available: Yes
htaccess rules: Custom rules have been added to your htaccess file

### Database ###

Extension: mysqli
Server version: 5.7.21-nmm1-log
Client version: mysqlnd 5.0.12-dev - 20150407 - $Id: 38fea24f2847fa7519001be390c98ae0acafe387 $
Database prefix: wp_boomenter

### WordPress Constants ###

ABSPATH: /www/htdocs/w00c5578/html/entertainment/
WP_HOME: Undefined
WP_SITEURL: Undefined
WP_DEBUG: Disabled
WP_MAX_MEMORY_LIMIT: 512M
WP_DEBUG_DISPLAY: Enabled
WP_DEBUG_LOG: Disabled
SCRIPT_DEBUG: Disabled
WP_CACHE: Enabled
CONCATENATE_SCRIPTS: Undefined
COMPRESS_SCRIPTS: Undefined
COMPRESS_CSS: Undefined
WP_LOCAL_DEV: Undefined

### Filesystem Permissions ###

The main WordPress directory: Writable
The wp-content directory: Writable
The uploads directory: Writable
The plugins directory: Writable
The themes directory: Writable

The page I need help with: [log in to see the link]