I created a site on a test domain, and now I want to cross the production domain on this directory. I know that there is a similar topic here: https://octobercms.com/forum/post/change-domain but there the solution is to move the whole directory under the domain. I want to do the opposite - I want to connect the domain to the directory. Unfortunately, when I put the main domain under the target directory, a "page error" appears. In the console, a page error appears: "Failed to load resource: the server responded with a status of 500 (Internal Server Error)".

Can someone help me with this?

check the directory permissions/ownership