Can't get TDM to work with VirtualKVM or Manually (iMac Late 2009 & MBP Mid-2014)

[smellsworth]

Here's the setup:

• iMac Late 2009, Mini-displayport, has wired Apple keyboard and wireless Apple magic mouse, High Sierra 10.13.6
• MBP Mid-2014, Thunderbolt 1/2 ports, wireless Apple mouse & keyboard separate from above, High Sierra 10.13.6
• Mini-displayport-to-Mini-displayport cables connecting them

VirtualKVM isn't detecting a connection. Any suggestions? Should I be able to see a connection in System Information on the MBP under Thunderbolt?