Hello Kevin,

Thank you for getting in touch with us!

Probably it cause by your server configuration. Could you please send me a screenshot about your LayerSlider WP -> Options -> System Status tab?

To find out the exact cause, we need to see the PHP error message.

PHP logging is almost always enabled and you can usually access the PHP error log files on the dashboard provided by your web server host. Another possibility is a "logs" folder, that usually located outside of your WordPress installation directory when you try to browse your server via a FTP client.

You can also contact the web host to look into this and make any changes that may be necessary. 

Hello Kevin,

Thank you.
Unfortunately, it is not entirely clear what is causing the error. Could you please send me a wordpress admin temporary to your site? I would like to check it.

Hello Kevin,

I tried to login, but I got this error:
Unbekannte E-Mail-Adresse. Überprüfe sie noch einmal oder versuche es mit deinem Benutzernamen.

Could you please check it?

Hello Kevin,

Thank you.

I tested the slider import and I got an 500 server error, but there is no concrete PHP error message which can help to solve this issue.

Please send me your PHP error log again(because the latest one contains other messages then fatal errors). This link will help you about how to find it on your server or please contact with your hosting provider about it.
https://docs.plesk.com/en-US/obsidian/customer-guide/websites-and-domains/viewing-website-error-log.73938/

I'm looking forward to your reply.

Hello Kevin,

Thank you.

The error message is related to mod_fcgid. So probably you should modify the "FastCGI timeout" value, which has the exact name "FcgidIOTimeout".

You may not be able to edit this on your server, so you should contact your server administrator about how to modify it.