armStone A5 in a Plexlog Datalogger

Hello, I have a Datalogger from Plexlog with an armStoneA5 inside that's not booting any longer. I'm trying to debug what the cause of the problem could be. There's two LEDs on the A5 that first light up both, then one of them lights up dimly and stays that way. On an second okay device, the second LED flickers activity after a short boot sequence. I'm trying to see if there's any helpful info on the RS232 port, but all I can't seem to get any output on both the okay and dead device in DCUTermi. Does anyone have an idea what I could try doing to debug this error?

I've attached two images of the good device (bright led, flickering) and bad device (dim led, static)

I've followed the guide and there's still nothing coming back from either device via the RS232 port, so I'm currently guessing that maybe the manufacturer (Plexlog) made changes to running firmware so it only outputs something if talked to first, with a specific string or something. Can't really tell for sure since there's no official documentation from Plexlog I could look into.

Does the armSTone A5 usually always output something on RS232 port when booting, or is it common for manufacturers to disable that functionality?

PLEXLOG says: No service, only B2B