I personally think Noob doesn't care at all. Once Noob was reborn in the Netherrealm, he no longer cared about Scorpion and he no longer cared about getting revenge, all he cared about was serving Shinnok.

Your title misled me...

But on the topic, I don't think it's really necessary for Scorpion to hunt Noob or vice-versa. He already got his revenge by killing him, and Noob has already embraced the darkness to give a shit about vengeance. However if Bi Han had also killed Scorpion's family and clan, I'm sure we'd see Scorpion pursuing him a lot more often (even though he's already technically dead).

He got his revenge by killing Bi-Han once, so there is no need to do it again, also in MK4 he found out Quan-Chi was responsible for the death of his family and clan (That's why he pursued him in the Netherrealm and that's why Quan-Chi got the two oni to protect him from Scorpion) so killing Bi-Han again for something he didn't do would be pointless, yeah Bi-Han killed Scorpion, but Scorpion killed him when he came back to life, so its kind of even lol

As for why Bi-Han as Noob hasn't attacked Scorpion, likely because he just doesn't give a shit anymore. He's all about Shinnok and the Brotherhood Of Shadow now.

I think Noob never sought vengeance because he liked what he had become. In MK9 when Raiden's warning Scorpion not to kill Sub Zero numba 1 he says something like he senses he will become a more powerful evil, it was something like that I think. So yeah Noob seems more concerned with power. I always thought that was cool about him, he's so cold blooded he doesn't give a fuck about being killed as long as its a means to an end. He has zero desire to avenge his own life and doesn't give a fuck about his Sub Zero legacy.

As for Scorpion I don't know if he ever knew that Noob was the original Sub Zero. Or at least by time he found out about Noob (if he ever did??) he had already realized Quan Chi murdered his family and therefore went for him and was even with Noob.