Electron breathing white - how to get to listening mode?

I am trying to use the HX711 with my Electron board and I got to a point where I have “breathing white” - which I believe means that the cellular mode is off.
I would like to upload a new firmware via USB, which requires listening mode (flashing blue), but even if I hold the MODE button for 3 seconds it never enters listening mode, it is either steady white or breathing white, nothing else.

Any idea how to get to listening mode from white?

Can it be placed in DFU mode?

Thanks, that did help to get out of the steady white / flashing white cicle.