UR44 USB audio interface announced

Hi stephan, i bought the ur44 and i am already stuck with a simple thing which i cant get going.

i connected the main output and line3/4 output with two pairs of active speakers and played some audio files with windows media player.
The audio signal is coming only through the main output and the headphones, but not through line3/4.
As i understood, the signal going to line3/4 output can be mixed in MIX2, but in MIX2 the daw strip shows no incoming signal, in MIX1 everything is fine.
Is it me, or is it the UR44?
I need to resolve that fast, because i still can get the UR44 back to the shop if it wont work.