According to an Improbable blog post today, their SpatialOS cloud based networking service is being forced to shut down by a change Unity have made in their terms of service. This means all games that currently require SpatialOS are also impacted. Other game engines such as Unreal Engine and CryEngine and open source engines such as Godot and Xenko are unaffected by the change. Unity have not yet released a public statement.
Unity have issued a response: