I had this issue prior to the 0.8.1.2 hot fix. I've been playing for 2-3 weeks since. Then this morning I can't start the game. Same error. "Waiting for response from Steam." then the error message saying Steam's servers are not responding. Other games do start up ok. Only affects RW.
I should add, that I played this just last night, and nothing changed as far as I know. It doesn't get past the opening logo screen.
My specs:
iMac (mid 2012) stop laughing, gamers.
3.4 GHz Intel Core i7
32 GB 1600 MHz DDR3
NVIDIA GeForce GTX 680MX 2048 MB
1TB Harddrive (SSD+mechanical combo)
OSX 10.11.6 El Capitan