Please give us, the users, an option to download all old versions of Piplay, due to unsolved issues with an every new one.
Best of the really old is piplay 1.1.92. You will find it in here.
Didn't help. Still getting an error 400 from SteamVR. It works only with Piplay 1.1.92
Its been awhile. Search the error. I believe thats a steam compositor error.
If you can post the error msg.ie even screenshot.