Completely exit from the Steam client.
Go to C:\Program Files\Steam (or the Steam directory that was specified during installation).
Locate ClientRegistry.blob and rename this file to ClientRegistryOld.blob.
Restart Steam to allow the file to be recreated.
Update:
You might need to apply the latest patch 12.0.3 which was released on October 27. Steam will need to be set to ONLINE mode to automatically update your game with the patch.
Go to C:\Program Files\Steam (or the Steam directory that was specified during installation).
Locate ClientRegistry.blob and rename this file to ClientRegistryOld.blob.
Restart Steam to allow the file to be recreated.
Update:
You might need to apply the latest patch 12.0.3 which was released on October 27. Steam will need to be set to ONLINE mode to automatically update your game with the patch.