if you don't have a splitter, tuners must be "connected" in the following manner:
C to A
D to C
E to D
This is as per instructions of Vu developers. Common sense suggests they were "connecting" to A, but that won't work.
I have used "connect" to signify the feature in unicable tuner configuration, not the real life meaning of connecting a wire. Hope that helps.
EDIT 05 Sept 2018:
This post was made for the Solo4k when it had a driver issue. The above no longer applies.
When selecting connected, you select the tuner with the actual signal wire attached.
C to A
D to A
E to A