Hi Uzi,
congratulation for the 1st User message posted in THIS forum!!!
As far as I know, QS-DEC-II are solenoid device decoders of LDT for the Motorola-protocol.
If you had no problems using these decoders with CU6021/6051 then there should also be no problem by using it with the IB!
The only thing what could be wrong is, that your IB is not configured for Motorola format as default. Then the IB will send DCC format to the decoders - and nothing will happen - really nothing
Just have a look in your IB-manual and change the data format for your decoders to Motorola.
Alternatively (just for test purposes) you can change the Digital System in your WDP system settings from "Intellibox" to "Marklin" - then it should work as well.
I recommend to check the first suggestion.
Regards
Rüdiger