Please fill out the fields below so we can help you better. Note: you must provide your domain name to get help. Domain names for issued certificates are all made public in Certificate Transparency logs (e.g. https://crt.sh/?q=example.com), so withholding your domain name here does not increase secrecy, but only makes it harder for us to provide help.
My domain is: marmorwelten.eu
I ran this command: certificate created by Plesk
It produced this output:
My web server is (include version): nginx
The operating system my web server runs on is (include version): Ubuntu 19
My hosting provider, if applicable, is: Strato
I can login to a root shell on my machine (yes or no, or I don't know): yes
I'm using a control panel to manage my site (no, or provide the name and version of the control panel): Plesk Version 18.0.52 Update Nr. 3
The version of my client is (e.g. output of certbot --version or certbot-auto --version if you're using Certbot): not available on Plesk
TSL works properly on Chrome and Firefox but I can't access the site using Safari. Checking the Certificate in Safari shows the default server certificate of Plesk which is used to secure the default domain and not issued by let's encrypt.
Checking with TLS Test results for marmorwelten.eu, [2a01:238:420c:5400:ee11:f968:da22:82e1]:443 shows also the wrong Certificate while checking with SSL Checker - Check SSL Certificate Installation of Your Site shows the let's encrypt certificate.
Is the webserver misconfigured or what's going on here? Any help appreciated!