I just updated to the Sensar Pro myself. My old unit had the typical Coax out on the front of the plate, a cable in on the back, an antenna in on the back, and a TV2 out on the back. The TV2 out went to a splitter just as your does, but mine was right there and so I connected the two outs from the splitter to the tv1,tv2 outs of the new unit. If you can get to you splitter, the if you connected either tv1, tv2 out to the cable that goes to the splitter, you should have things hooked up.
One thing to check, your old unit had a button you pressed to turn on the power to the antenna. The Sensar Pro does not have that same, simple deal. You have to cycle thru the settings until is light next to Park Cable is illuminated. Did you do that?
And lastly how was the cable reception before at this site? Could it be poor cable service? Have you checked the external connection for corrosion?