I created a Rift application on the Oculus Dashboard for debugging. The first time I launch a PIE instance the entitlement will succeed and I can perform a request, such as getting all of the friends; however, once I stop the first PIE instance and launch a new one I get a warning and I cannot perform a Platform SDK request.
LogOnlineEntitlement: Warning: Oculus: Oculus platform service not available. Skipping entitlement check.
If I restart the editor and launch a new PIE instance, it will succeed.