Maybe whenever I next pay a visit to LV with a vehicle and cash will I go and ask the attendant if I can pay with cash and then use the B-Connected card to get the additional discount.
I just learned a tip that might help some people. I, too, have had some problems with getting a discount. I mentioned this to a Rebel clerk and he said to only use the old red cards. I found one of my old cards and, what do you know, it works. Has ever since. My blue Sapphire never worked. Hope this helps.
And also people can keep in mind that (I think that this promotion is still going on as well) if you go to a Las Vegas Terrible's Connected Gas Station (like usually Chevron's -- and you should also see a small Terrible's sign there, if you pay for gas and then take the receipt to Terrible's LV Casino, they will credit your Slot Club account with one point per Dollar of Gas Paid.
So what this means is that if you paid $40 for gas, then your account would be credited 40 points. They have to keep the receipt and so I would recommend that you get a reprint of the receipt while you are still at the gas station.