Hi there,
We have seen this a few times in the past and although we cannot pin down a real issue, we have had some success with updating the network switches to handle the auto-discovery better. (We all rarely remember to update those Switch firmwares.)
Also, if you can try and connect the MOM to a single computer without any other network units on it, see if you can see the MOM show up and then check if the Network Settings are not clashing with an existing unit.
If this fails, then drop us a line on support@ntp.dk
Best,
Jon