You were not "IN" launch control, you probably did not go to WOT fast enough. That is not your fault there are some inherent problems with the current set-up.
IMHO SRT has to do the following:
A, Increase the allotted time from when you hit the Launch Control button till you go WOT.
B. If you go beyond that allotted time the prompt to enter launch control disappears.
C If you are successful in entering Launch Control, there is an indicator on the dash similar to the glowing snake.
D. Allow a manual preset selection of the amount of slip.
Tried it 3 times yesterday, and I was not succesfull.
Got alot of tire spin/ smoke each time and the car started to go sideways. Once floored I let go of the clutch within a second or two, do you have to wait longer or for a message to say it's ready ? I did not look at the cluster.