On 2/18/2019 at 4:15 PM, Bocco said:OK, I think I have found solution. As @wmh90 explained problem derives in deleted languages which still remain in database.
First of all make backup of your web shop before you make any changes.
Go to backoffice to International/Localization/Languages and check for Id of languages installed.
Log into cpanel, phpmyadmin and locate your database and then search for psfm_meta_lang table. Open it and filter id_lang by ascending number of Id. Delete all pages of id languages you don't need them.
Then go to backoffice of your prestashop store into Traffic&SEO. Now you can edit URL pages. If you have to use more than 1 word in rewritten url, use sign - between words, for example: page-not-found. And use only english letter a-z.
Thanks @Bocco! That works for me. It's a bug of PrestaShop: when you delete a language that you are not going to use (from International > Localization > Languages), you got a message sayng "When you delete a language, all related translations in the database will be deleted."
https://pasteboard.co/If6sXBJ.png
But that does not happen. PrestaShop keeps the "deleted" information in meta_lang table and that generates a conflict when you try to edit a page from URL & SEO area.
My solution was listing contetnt in DB for language IDs and delete all elements with language IDs I was not using.
https://pasteboard.co/If6xUVa.png
