First, check the following:
-Check if your GPU meets the GameStream requirements. You can get this information under, Settings > General > Features.
-Check if MSVC Runtime package version 12.0 or higher is installed for both 32-bit and 64-bit architectures. You can view this information under Control Panel > Programs and Features. For details, refer https://support.microsoft.com/en-in/help/2977003/the-latest-supported-visual-c-downloads
-Check if there is any active remote desktop sessions on your PC.
If the problem is not solved, try the following steps:
-Open Task Manager.
-Check if "NVIDIA Web Helper.exe" application is running.
-Under "Services" tab, check if "NvContainerLocalSystem" service is running. If not, right click and select "Start Service" to manually start it.
-Still not fixed? Send feedback via GeForce Experience (under GameStream category).