NVIDIA has stated that they are working with Paradox to resolve the issue.
Crusader Kings III and Stellaris in maintenanceInvestigating - We are currently working with Paradox to resolve an issue affecting both Crusader King III and Stellaris. We will make them available to play as soon as the issue is resolved.
Jun 30, 09:40 PDT
We will update this article when there is an update from NVIDIA.