Problem to Translate

hi,
the site is on maintenace mode. So, i follow the guide but when i choose the language, it appears this problem “Loco requires the “%s” PHP extension. Ask your hosting provider to install it” .. the hosting provider tell me that this extension is installed!
Can you tell me how i can solve this problem? Also i need to insert the language flags in the header, i can do it?
Thank you

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