Christiian,
When you look for the traffic, is it on the external (Internet) side of the firewall? If so, Multitech can take a look on Device HQ and see if there is any reason that the device(s) cannot establish a check-in session. If nothing is coming back from Device HQ on the Internet side, please file a Multitech Support Portal case at https://support.multitech.com and someone can help you.
Thanks,
Jeff