I have one sub site ... lost

hello.
I have loss admin and the site
http://olistiki-diatrofi-adinatisma.ygeia-enarmonisi.gr/
I did a upgrade to a theme and it fail. it was not the theme of the site. The site ( with the problem is Extra) i did upgrade Divi and fail.
i have admin of the multisite and i have enable support.
Thanks a lot