Fathom-X no Link establishment / connection

Hi everyone,

we bought a fathom x single board and an and fathom x interface (fxti).

But we just don’t get the single board to be recognized at out computer. When we plug the fxti via usb or directly via ethernet into our computer we see, that it is recognized as 100/10 network. When we plug into our single board our network just shows “plug not connected”.

First we thought it was our rj45 socket as we got the version without socket and had to solder one by ourselves. But there is no shortcircuit between any pins. pf-td+ to pin 18 has 0 Ohm , to pin 17 it has 100 Ohm, pf-td- the other way round. Same for pf-rd+ 0 Ohm to pin 15, 100 Ohm to pin 16ten and pf-rd- the other way round. Vdd2p0 connects with 0 Ohm to pin 14.
Selfcheck LED (Pin 10)has 3.3V to ground.
PWR led is on all the time.
The link LED (physical) is on at the beginning, after 3-4 seconds it is off (does not matter if we connect the ethernet and/or tether or not ). the led link pin (pin 9) has 0,17V when its on, 3,3 when its off.
Pin 12 (led act) has 0V all the time.

of course we de-soldered our rj45 socket and tested those things with and without socket.

Are there any other tests we can run or check?

p.s. test results are the same with 12v battery input as well as power via usb

Ok, with some linux computers we get the message “active connection removed before it was initalized” maybe that’s a hint?