At this point Kylo Ren has already sensed Han's presence on Starkiller Base. When Kylo is on the bridge, Han is standing a stone's throw away from him, yet Kylo doesn't sense him there and Han has to yell to get his attention. Is sensing through the Force so imprecise that even when someone you're looking for is standing in close proximity you still only have a vague feeling that they're somewhere on the planet?!
Despite their close familial link, Han proved difficult for Ren to track because he was intentionally concealing his presence in the Force by exercising strong control over his thoughts and emotions.
Here, Ren told himself with increasing certainty. He is here. Raising his gaze, he focused on one support column out of many. Slowly he advanced toward it, prepared for whatever might ensue.
Nothing did. There was no one behind the column.
Rising from his hiding place, Han looked back the way he had come. If he left now and managed to control his thoughts and emotions while retracing his steps, there was a good chance he could make it out of the building. If he was really lucky, he would be able to slip outside without drawing the attention of any searching stormtroopers — or anyone else.
It would seem that although Han has all the Force ability of a turnip, mental concealment isn't actually a Force talent and is evidently something that can be mastered by a non-Jedi.