They don’t work together. Which is a pity for a system so expensive – but also not a surprise given the overall poor user experience (UI, ease of use) with the product.
The solution: Sabrent Wi-Fi Audio Receiver which is out of stock on their website but may be found reconditionned fe. on Amazon, costs 20 euros and fills the gap.
Bonus point: can be USB alimented by the unused USB port on the back of the system.