I'm looking to mirror a distinct body about a plane. However, when I open the Mirror tool to do so, there's no option to select bodies to mirror (see second screenshot). And yet when I execute the command, the mirror feature shows up with the error icon in the first screenshot, wherein it ironically recommends that I use the "Bodies to Mirror" option!.
Am I missing something? Should I do something to make the Bodies to Mirror option appear?
As always, all help is appreciated

Thanks,