Thank you..
When I play on channel 1, all the drums play. When I play on channel 1 1-6 mode, they play only one sound per track like you described. The drums work on the sequencer tracks, but I cannot get it to work either way you described using the dedicated drum track. No matter what channel I assign to.
Bizarre. I just double checked and had no issues with any MIDI channel I set the Volca Drum to. I made sure my VDrum was set to RxShortMsg and ensured I had a custom drum map set on the KSP (Part1: 60, Part2: 62, Part3: 64, Part4: 65, Part5: 67, Part6: 69). Tested Ch1, all was good, then tested Ch10 and all was good. You do have the latest firmware for the Volca Drum? I only ask because I can't remember what would happen when I tried to boot into the channel selection menu when I had the release firmware and the single channel mode was broken. But if you were stuck in split mode you'd most definitely notice.
Plug the KSP into MCC and open the MIDI view. Run a pattern on the Drum Track, mute the rest and see what is show up in the console. You should see the MIDI notes showing up if all is good on the KSP end.
Try setting Track 2, 3 or 4 on the KSP to the same channel as the VDrum. Select arp and play an nice close set of notes starting with middle C in (to match the notes expected by the VDrum). You should hear something out of the VDrum. If you have another sequencer or controller keyboard, do the same thing with it to see if the VDrum responds.