Just fyi, this is a sub forum for dealer and pricing discussions. You may want to post questions like this in the general forum for better exposure.
So, I'm going off of memory, but I don't think there is an audible beep (horn doesn't honk ever) when locking the car. It does beep when you unlock. But none of that matters for remote start. As you mentioned before, simply press the lock button, then hold the start button for 2-4 seconds. If that doesn't work, then take it to the dealer.
Does it start when you use the app?