@ Thank you for your time checking my issue.
I dont have build.cs they only file i have is: VRExpansionPlugin.Build.cs which I assume is ok.
I tried to download again SteamVR__1_11.zip and didnt make any changes but still I have the same error. is it something on my machine? Anyone else are able to package the project without a problem?
Thanks a lot,
Doron