Hi there! Error code CAT can occur if you did not receive the update for Destiny 2. If the issue is persisting, please close your Steam application, then reopen it. If the issue persists, please try changing your update priority for Destiny 2 to Immediate Download. This can be done in the Properties pane for Destiny 2, under Update. Then, change the priority to Immediate Download. If the issue persists, please contact Steam Support, as there may be an issue with the CDN you are trying to download the update from.