Default-language homepage incorrectly redirect

Hello,

I’m experiencing a redirect issue . Our original website is in Polish and is hosted at the root URL. After activating WEB-T, visiting the homepage automatically redirects to http://www.website.pl/pl/ , which returns a 404 error

Configuration:

• Default language: Polish
• Polish slug: pl
• Additional language: English (UK), slug: en
• Use a subdirectory for the default language: No
• Force language in custom links: No

Tried:

• Resaved WEB-T settings and WordPress permalinks.
• Tested in private browsing.
• /?test=123 redirects to /pl/?test=123.
• Deactivated Simply Static: issue persists.
• Deactivated WEB-T: the original homepage works normally.
• No other multilingual plugin is installed.

The issue also prevents us from using the WEB-T translation editor because the homepage redirects to a nonexistent URL.

Thank you in advance!