multiple USB streamer connections to SigmaStudio


We are looking for some workaround of two USB streamer connections to SigmaStudio. Three ADAU1787 are connected to each of USB streamer and We'd like to connect two USB streamers to SigmaStudio. 

We were able to drop USBi in Hardware configuration window in SStudio and connect three 1787 to each of them. Both USBi are green, indicating that both of them are connected.

Also, We saw six IC configuration tabs at bottom so that all six DSP registers can be configured.

However, it cannot make "compile and download" - always showing connection error.

Isn't SigmaStudio able to connect multiple USB streamers? Is there any workaround to make it work?

Any feedback would be appreciated.

Thank you