problem with pages

WordPress 4.0 with Elbee Elgee theme used and Ceceppa 1.4.27 version.

backoffice
I use two languages, italian and french.

I add a new translation for an italian page and I have no problems, all seems to be correct (both flags are displayed) on the dashboard.

frontoffice
The italian page goes directly to the main menu.

When I choose the page with italian language selected, all is correct (http://www.simoneaparigi.com/wordpress/benvenuti?lang=it/).

If I move the cursor on the link for the french translation, I can show the url related and it appears with “?lang=it” that is wrong, and if I click on it I obtain the [page not found] error (http://www.simoneaparigi.com/wordpress/a-propos?lang=it/)

If I edit the url on the address bar, modifying “?lang=fr”, again I got the [page not found] error (http://www.simoneaparigi.com/wordpress/a-propos?lang=fr/)

If I remove the parameter “?lang=..”, I got the right french version of the page (http://www.simoneaparigi.com/wordpress/a-propos/)

The strange thing is that this only happen with pages and not with posts.

Can you give me a tip to solve this? Where I’m wrong? Setup problems? Permalinks are setup to “/%year%/%monthnum%/%postname%/”

Thanks in advance

https://wordpress.org/plugins/ceceppa-multilingua/