When you say BeastX do you mean an actual BeastX and a separate Rx or a Spektrum AR7200BX? Assuming the later, you need to jump through some hoops because the 7200BX needs to see a low stick throttle input before it will init and then start sending signals to the ESC. The reason the ESC isn't initing is because the 7200BX isn't initing.
On my helis so far with a 7200BX I've always had the ability to power the 7200BX independently of the ESC (not using a built-in BEC on the ESC). With this kind of setup it is fairly simple:
1) Power up the 7200BX with a separate power supply (battery pack into a independent BEC powering the 7200BX in my case). With Tx throttle end point low set to something low and stick at low, 7200BX completes init (servos dance).
2) Move Tx throttle endpoints (low and high) to midpoint, move stick to high position (linear curve).
3) Plug main pack into ESC.
4) Complete endpoint setup as you indicated (move high endpoint up until beep, add a few points for safety, low stick and move low endpoint lower until init beeps, plus a few points for safety).
If you are powering via a built in BEC in the ESC, you will need to either use a separate power source with a servo lead on it to plug into the 7200BX to get it powered up and inited as described above, or maybe...
I've never tried this, but it should work. Again, remove blades and be ready for unexpected spin up and need to unplug the main battery quickly.
Pull the signal pin from the throttle lead servo plug going from the ESC to the 7200BX (leave red and black connected since it powers the 7200BX). Pulling this pin will let the 7200BX init while the ESC holds in limbo waiting for a signal. Plug in the main battery pack. Once 7200BX is inited (using Tx as described in step 1 above) and the Tx is back to midpoint setup (step 2), plug the signal line into the servo plug (must remain plugged into the 7200bx, so this may be difficult, and the noise it generates may confuse the ESC or even cause endpoint settings to lock in). Then complete the steps.
This should work, i think. At least as long as when you plug in the signal pin it doesn't generate a ton of noise.