On 200 model systems, the 5.0 plugin, combined with the latest System Software, should distinguish L/R automatically. If you're on 220.127.116.11745, that should be sufficient.
When the unity app is launched, does the screen appear to dim at all? That's a sign that L/R detect is being run. Knowing whether its being run will help us narrow down what's wrong.
Either way, I'd try reinstalling System Software from this link and see if L/R detection shakes loose.