Portal: Singularity Collapse download issues

[Realms×Myths]

As of time of posting, the mod "Portal: Singularity Collapse" is unable to be downloaded.
Attempting to do so causes this error:

An error occurred while launching this game: Game configuration unavailable

Mod in question:
https://store.steampowered.com/app/2882850/Portal_Singularity_Collapse/

Can anyone do anything about this?

[cali6pack]

Oh yeah thats because there isnt a download yet but steam glitched it even though you cant download it im in their discord