I've switched to "Different languages in directories" again for another test here hidden link using the Language URL format option.
Upon reviewing, if you visit this link hidden link , it displays the English language version of the site. And changing the language using the language switcher at the bottom worked well.
However, when you visit this link hidden link , it still shows a site from another server, as it's not reflecting any changes I've made to the hidden link site.
You need to check on this. Do you have another WP installation for this domain? hidden link
Yes, it looks like we're going around in a circle and there is no solution yet. Please create a subdomain as follows. Make sure there is only one WP installation and both pointing to the same new server.
hidden link - Japanese Language hidden link - English Language