Having trouble adding another language

Hello,

I am trying to setup the German language for my blog. I already have Greek working (ahealthcare.gr/blog) and English (ahealthcare.com/blog. Please notice that the English version is from a .COM domain,

Now I would like to add German to ahealthcare.com/blog so I thought I have to go to Languages > settings and type for Deutsch (German) this:

https://www.ahealthcare.com/blog/de for the german language but when i press SAVE I get this werror message: Polylang was unable to access the https://www.ahealthcare.com/blog/de/?deactivate-polylang=1 URL. Please check that the URL is valid.

The other settings are:

URL modifications

 The language is set from different domains

EN https://www.ahealthcare.com/blog

GR https://www.ahealthcare.gr/blog

Can someone please advice on how to set up the third language?

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