When I try to to set the quotas for a domain, I'm receiving the error like: "Disk space: requested - 250MB, maximum available - 0MB".
Every client and domain in Plesk have disk limit settings. Sum of domains' limits cannot be more then clients limits these domains belongs to. This error may occur if clients limit for disk space is exceeded.
You need to increase disk space limit for the client the domain belongs to or decrees disk space limit for some another this client's domain.