If the server is not down (see announcements) then this could be because the domain name has expired.
If domain names are registered through Platypus, we take all possible steps to remind the owner of renewal date.
We don’t pay for renewals until we get paid by the owner, just in case the owner has decided to let the name go. (This has happened).
If we pay to renew a domain name we get no refund if the name is no longer required.