Adding subdomain in plesk gives
Error: Unknown error 0xC00CE505 (COM Error C00CE505) at setScriptMaps(test55.domain.com, ) (Error code 1)
Login to plesk server – Vhosts – domain.com(problematic domain)
Open the .Plesk folder , (if its not showing , View hidden files)
You will have a .security file
Take a back up of the file and remove it.
Now it will allow you to add Sub domain