User page gives 404

The user page isn’t working; the website is in four languages. They use Loco Translate and Polylang.

When I go to the account, it works. Other pages work as well, as far as I can tell. However, the user page returns a 404 error. So it doesn’t exist. This could be because there’s a “Language” slug, but even then, I’ve read everywhere that multilingual websites shouldn’t be a problem.

When I click “View Profile,” I get the error message if I switch to a different language. The URL isn’t adjusted for the language in question, even though all the files have been created for all languages.

For language 1 (Dutch), I’ve set everything to default in the settings. Strangely enough, it picks up language 2 (English). I can edit my own profile by editing the URL: “en/user-en?um_action=edit”

Despite having admin rights, I can’t view or even edit someone else’s profile. For .nl, a username is immediately added, and in this case, it’s my own “nl/user/admin/”.

Is anyone familiar with this problem or knows a solution?

The page I need help with: [log in to see the link]