I'm having exactly the same problem with my new erisin 9015, all plugged in correctly & secure, built in can bus, so wiring was a doddle just the lockdown latch thing, but it works internediatly, I never unplugged my hazard lights switch,as I read I could throw up a code that needs a re set by vag com.
Never had a moments trouble with the rcd 300.
I think these units are a good idea, but in reality they simply don't pull it off.