Add Device, Device added successfully but cannot be found

I'm evaluating OpManager and just installed the server. I added two Windows 2003 boxes and two switches and it works perfectly both with WMI and SNMP.

I then tried to add a specific temperature/humidity monitor from Black Box called Servsensor Junior. I use "Add Device" and it tells me "Device added successfully" but it never shows up in OpManager.

I've made sure that SNMP is enabled and community is set to "public". I can ping the derivce and do a "manual" SNMPget from commandline to confirm it's really working.

Tried re-starting the server, adding it again, waiting for a long time - it never turns up.

Any suggestions?

More info on the Servsensor:
http://www.blackbox.fi/media/products/pdf/41389_en_v10_m56577569830478239.pdf

Product manual:
http://87.236.254.72/manuals/E/EME102-Manual.pdf