- you can check on the Performer side: the mic and/or Instr channels should show meter activity (and thus, master too) to indicate that the hardware signals come thru. Without that, nothing can come thru to Cubase.
- if those meters move when a signal is applied, Studio should hear it thru the VST Conenct Monitor plugin in the Control Room Monitor channel at any time (“From Performer” should of course be raised). Unfortunately there is no metering for that. If Studio uses headphones, the VST Connect Monitor plugin may have to be moved to after the Hedaphone Monitor instead.
You may then (if 1) applies) also try to engage the Performer Track Input monitor, even though this is explicitly not recommended (huge delay), but at least then you can tell if those signals arrive at the Studio.