one of subdomain not working

I fell blog [www.eryniawtrasie.eu] the fault of the hosting (set the wrong version of PHP), we managed to restore the blog to life but stopped working sub (subdomain) [www.przydasie.eryniawtrasie.eu]. I can not even go into the cockpit. I can create a new site with a different name and there is no problem with its filling or access to the cockpit but change its name to ‘Przydasie’ is no longer visible, there is even a possibility to enter into the cockpit.
What should be changed to make it possible to create (restore) a subdomain [www.przydasie.eryniawtrasie.eu]?