Don't bother tapping Ludicrous+. You have to either tap and hold the Ludicrous+ button for 5 seconds, or just go to the toybox and tap the starfield picture/button. Doing either of those things will bring up the special Bring it On prompt. Just tapping Ludicrous+ and waiting doesn't activate full power or launch mode - it just heats the battery.
Mine doesn't work that way. Tapping Ludicrous+ brings up the Max Battery box and tapping the starfield in the toybox brings up the same Max Battery box. Doing both enables launch control and starts warming the battery. I never get the Bring It On box. I'll try to post a video.