Different domains with polylang not working

Hello guys,

I am afraid I am going to need your help with setting up polylang on different domains.
Currently I have a website in development and once it is going to go live, it will have two different domains. .cz and .com.

Here is the main czech development version: https://weddev.cz/flera2/
Now what I am trying to achieve is to have the english version in different subfolder, so the domain is https://weddev.cz/fleraen/.

Just as the guide about this says, the domain fleraen points to the folder where the original https://weddev.cz/flera2/ is. Even if you open the english version, you can see the czech version of the website there with a 404 error. Which I believe is correct as the URL actually does not exist. But the problem is that when I try to activate the functionality in polylang, I get this message:

Polylang was unable to access the https://weddev.cz/fleraen/?deactivate-polylang=1 URL. Please check that the URL is valid.

Any suggestiones how to solve this?

Maybe should the fleraen domain be setup as alias for flera2?

Or some other solution. There is not enough information about this issue around.

Thank you,

Josef

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