Make sure your LCD/liveview is set to do
exposure simulation. Then crank up the exposure settings until you can see what you've got. Most LCD/liveview will also let you magnify the view, so you can magnify on the portion of the image that's important to you, then use the focus ring on the lens to fine-tune (obviously, set the lens to manual focus, or half-pressing the shutter button make refocus the camera).
Probably. It could also mean your camera isn't set to do exposure simulation in liveview as well as that your camera exposure settings were too low to get a good exposure. I'd say, start at iso 1600, f/4-8, and maybe 10s and see what you've got. Remember, 12 stops isn't 12x less light. It's 2 to the 12th power (2^10 -> 4096)x less light.
BTW, here's
a list of known good/bad lenses for IR in terms of hotspots.