I had a similar issue with a brand new RS. I installed it in my car, did the initial endpoint setup and then hooked it up to my hotwire to tweak some settings.
The hotwire software said the software on my esc was out of date and would update. Appeared to go fine, but then when it rebooted the esc the software couldn't find it. anymore This left my esc in a similar condition to what yours is in.
I was able to connect to it with the hotwire, but every time it kept popping up a warning window saying something along the lines of 'some parameters are invalid'.
I kept trying to load defaults from within the Hotwire software, tried two different laptops and eventually it began working again. I'm not even sure the sequence of events that made it start working but it finally did, but if you can get into the hotwire interface, try resetting to defaults or updating your esc software to the latest.