Internal Server Error - Again

[SuiCo]

Hi forum
As I saw there are many solutions against the short error messages.
I tried all the solutions but without any changes.

I did:
- Unchecked Short HTTP Messages in Browser (I also restarted the Browser)
- Change 500 Error Output to 'default' in Plesk->Domain.tld->Directories->Error Documents->500
- Change CustomeErrorMode to Off in ASP Settings
- Unchecked Custom Error-Documents in Plesk -> Webhosting Settings
- Checked Permissions
- Reconfigured vhost
- Restarted App and Website in inetmgr

Still the same 500 Internal Error, what can I do?

Best regards
SuiCo