[Closed] my default language site /en/ as well as translated site /da/ are all in 404 er

I am trying to: load the default English language site /en/

Link to a page where the issue can be seen: hidden link

I expected to see: the front page I have developed

Instead, I got: 404 error page

Additional information: I have the duplicated test site which is locked to admin access. When I login and check, the default English website is working. When I switched the production site theme to Twenty-Three (WP default theme), the /en/ is still in 404 page, but hidden link is showing the theme designed page.

I have the communication log found in the support section in WP backend, but I cannot paste to the Debug info, therefore, I paste here:

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