Server errors are almost always caused by misconfiguration of Grav. Something unexpected happened and because of that Grav is unable to recover and serve the page.
When you see this message it means your server is running in
Production mode to hide potentially sensitive information from displaying to your users. The error itself will be stored in the
logs/grav.log file. Please examine this file to determine the exact nature of the error.
Possible reasons include:
If you have the Grav Administration plugin installed, you can browse the Server Errors from there. By clicking the individual errors you can see the debug pages even if the debugger was turned off.
The first thing you should do is flush the cache to ensure that the configuration is up to date:
Before moving on, make sure that you do not have other file permission issues like this.