HL7800 and mangOH Green - unsucessful and confused, no comms

I am doing personal research on the topic, considering switching to using Sierra IOT module which is a free-tine training I might use in my company.
I have mangOH green which is working, as I have managed to capture via RS232 entire booting sequence using serial port and WP8548 module - no problem.

On the other hand, I have ‘borrowed’ brand new and fresh Sierra HL7800.
Following the advice i have bought TCL-HL78-2153 adapter which is just a frame centering the smaller HL7800 in larger CL3 socket, while the corner is clearly marked with a hole in module metal case so there is no mistake. Still, there is some perceivable horizontal play (0.5mm movement withing the plastic adapter frame). But nevermind, I have bent the metal shield holding the chip in the socket so that it pushes it down more firmly than with larger and thicker WP8548, and put it carefully centered.

Now the problem:

  1. Still no answer from the module whatsoever, but it is not smoking nor heating
  2. I have learned that HL7800 has been phased out by HL7800-M at digikey, so it might be pointless to waste time with the older one
  3. I am about to assume my HL7800 is broken and order HL7800-M but before I would like to make sure I I haven’t overlooked something

Honestly I would expect some output on the serial port (as with Cinterion wireless modules):
-either linux boot-up sequence messages
-or response to AT commands, ar any glith coming out of RS232 - but nothing at all can be seen

I expect HL series to be AT-command-driven modem using

Anybody has any advices why I cannot communicate with it using mangOH green?

We don’t support hl78 plus green combo. If you want to use hl78 with mangoh, please use DV6 mangoh red