Hey there. At the beginning of Beyond Light, a bunch of content was added to the Destiny Content Vault (DCV), including the zero hour mission. As a result, the catalyst can no longer be completed. You can find more info about the DCV here: https://www.bungie.net/en/Explore/Detail/News/49189 Bungie has said, however, that the catalyst will return at a later date with new objectives, so stay tuned.