There was a bug where if a Cisco Switch and QSYS Core booted up at the same time, the VPage or VCom would look like it was offline (all LEDs on the buttons would be off, and it would be unresponsive). Rebooting the VPage or VCom would not fix the issue, but rebooting the QSYS Core would.
This bug is resolved by making sure your VPage or VCom firmware is on 2.15.05 or higher, as well as your making sure the VPage / VCom plugin in QSYS Designer is also at version 2.15.05 or higher.