“That means every vote the North Dakota Senators ever voted on is void!”
No, but maybe everything one or both of them voted on that passed by a single or a couple votes.
No, a technical irregularity will not void a states admission, it did not for Ohio in 1953, it will not for North Dakota in 2011.
Every act by North Dakota’s government and Congressional delegation is fully lawful. One missing word cannot void the clear will of the Congress and the people of North Dakota.