The Hedera testnet had an incident yesterday which resulted in approximately five hours of downtime (for testnet only). The issue arose in the centralized management of testnet. It was fixed, and testnet is now running correctly. No data was lost or corrupted. This was not caused by any code bugs, and does not affect mainnet.
Engineering and DevOps will be conducting a root cause analysis around this issue to better understand how to prevent these issues from occurring in the future.