The Windows App SDK Runtime version must be the same as the Windows App SDK NuGet Package version
Currently, both must be 1.1.0-preview1 :
Installed Runtimes :
C:\Program Files\WindowsApps\Microsoft.WindowsAppRuntime.1.1-preview1_1000.447.2307.0_x64__8wekyb3d8bbwe
C:\Program Files\WindowsApps\Microsoft.WindowsAppRuntime.1.1-preview1_1000.447.2307.0_x86__8wekyb3d8bbwe