Weird Message trying to load Hammer

[lonefox]

After the update I tried to open VHE and I keep getting the same error: "MountFilesystem( 321 ) failed: SteamMountFilesystem(2348,321,0x380fbfc=,0x380fd0c) failed with error 5: No CS online with App 321 Ver 5."

Any idea on what it is and how to fix it?