Blockchains are designed to be highly resilient and fault-tolerant due to their decentralized nature. If a blockchain goes offline, it is likely a temporary issue, and the network will recover once the underlying problem is resolved. However, in the unlikely event of a major failure or loss of consensus within the network, the domain names registered on that particular blockchain may be temporarily or permanently inaccessible, depending on the severity of the issue and the ability of the network to recover.