How is the night king not at the wall yet? [duplicate]

Question

In episode 10 of season 2 we witness the encounter between one of the Night King's "officer" and Samwell Tarly.

However, since then, Samwell had time to make it back to the wall, meet Gilly and her child, leave the night's watch, travel it to the Citadel, study to become a Maester, leave the citadel etc.

Now, even after all this time, we see in episode 6 of season 7 that the army of the dead has not even reached the wall yet. Considering the fact that the army of the dead is made out of undeads who don't need (or at least I don't think so) to frequently stop to eat or rest, I was wondering how they haven't made it to the wall yet.

I thought that they maybe could've been retained from heading to the wall by the some of the 3 eyed raven's magic, but even then, Bran had the time to make it back to the wall by being pulled by a young girl on a sled.

I feel like I am completely missing out on some basic plot hole and that this question is actually super easy to explain but unfortunately, I truly cannot recall any events that could explain this.

Edit: Regarding the accusations of this question being a duplicate of (Why is the Night King so slow?). From what I understood, that other question was addressing more precisely why the night king ACTS as slow as he does, notably in ep6 of season 7 when he attacks Viserion. My question is more looking at why it took the night king more or less 5 seasons for him to reach the wall while Samwell did it in barely 1. I researched before posting this question and unfortunately that other question did not answer at all what I am asking here...

Answer 1

It's hard to say because we really don't know what he's been doing exactly or why.

He could be waiting for winter as he needs a way around/through the wall and waiting for the ocean near Eastwatch to freeze would allow him to walk around the wall. Or now that he "marked" Bran he is going to be able to break the magic barrier of the wall the same way he broke the barrier around the 3 eyed raven's cave.

But a likely explanation is that him and his army simply move at the speed of plot. So he hasn't made it there because it's not time for that in the story and it's just a plot hole.

Answer 2

Are we certain that he will attack the Wall at all? What we know from the show is that he obviously doesn't go directly south towards the wall and he is not hasting at all. Going from the Fist of the First Men to Hardhome is nowhere close to heading towards the wall - actually he was going more or less to the east, parallel to the Wall. He also made a huge detour to kill three-eyed raven once he marked Bran. And now he bides at that arrowhead mountain that Hound Clegane saw in fire.

So without specualtion, it is clear that his goal is not to storm the Wall as soon as he can. His army of wights is very slow indeed, but that's not the main reason. He is doing some things north of the wall, actually we don't know but only expect (as everyone in Westeros) that he wants to attack the Wall. He cleared the lands north of the Wall of living and is now amassing his wights from all over the palce. He might just wanna capture the Wall and set up "White Watch" so living will no loger be able to pass the Wall to the north and bother him :)

So the short answer is that he is not at the Wall because he doesn't want it yet. And he did a lot of stuff north of the Wall first. Is he now just waiting for colder days, is he simply amssing all the corpses he can, did he lured Jon and Daenerys into trap to get a dragon, is he digging and underground tunnel... we can only specualte until we find out. But since there is only one more season to go, we won't have to wait much longer.

Answer 3

Now that he has a dragon he can fly over the wall. There is speculation that the wall has magical powers that keeps him from passing trough it. It's not known if he can see the future with his connection to Bran and if he knew that he would be able to acquire a dragon.