Ableton Forum

Ok I managed to get it working.

Here's what I did:

1. turned off the push
2. plugged in my sustain pedal in "2" on the left
3. i held the sustain pedal down with my foot
4. turned on the push
5. released the sustain pedal once it was fully booted up

Just to say that with firmware 1.4.0 it is working correctly for me.
Pedal plugged in Pedal 1, Settings > Pedals & CV > Pedal & CV 1 set to Trigger
It starts and stops recording on press, perfect!