I have seven machines and use a KVM pro license which should support up to nine. The lay out is kind of a 2x4 grid but one is just one machine with dual monitors.
X X X
X X X X
The machine in the very top right is not working. I have verified that the multiplicity software on the host can see it during scan and can add it with the passcode. It then lights up like the other machines just fine. However I can not move the mouse to it via the machine blow or to the right.
I use this software often so am not new to it. I have rebooted several times and even given it time to settle which seems to matter. No clue why this one machine seems connected on the host and client side but does not actually work.