You probably figured it out by now but for others (like me a few minutes ago):
You need to add a channel. I did it using Virtual Maschine Manager:
While on viewing details for the opnsense virtual maschine click on "Add Hardware".
Select "Channel"
.
By Name open the drop-down-list and choose "org.qemu.guest_agent.0"
Next 2 were autoselected:
Device type is "UNIX socket (unix)
Check-box "Auto socket" is selected.
Click "Finish"
Reboot
You need to add a channel. I did it using Virtual Maschine Manager:
While on viewing details for the opnsense virtual maschine click on "Add Hardware".
Select "Channel"
.
By Name open the drop-down-list and choose "org.qemu.guest_agent.0"
Next 2 were autoselected:
Device type is "UNIX socket (unix)
Check-box "Auto socket" is selected.
Click "Finish"
Reboot