Question about Samsung QE55QN95B

Top delivery, reasonable set-up and somewhat lengthy installation, but everything is fine so far. And now I want to connect the Swisscom TV Box (IP1400), but the Samsung TV doesn't recognise it. During automatic recognition/setup there is a black screen at some point and during manual setup the corresponding points are missing in the selection and then it doesn't go any further ;( . Tested all HDMI connections and two different cables (original from Swisscom and another one), nothing changes. Does anyone have any idea how I can proceed? And no, I don't actually want to watch TV via the BlueTV app ;) . Thanks in advance!