Hebrews 9:27 And inasmuch as it is appointed unto men once to die, and after this comes judgment;
This verse teaches us that every person must physically die once. It does not teach a person cannot die twice. The natural order YHWH put in motion is that every human being will die a physical death. However, in Lazarus' case, for example, YHWH broke the natural order by resurrecting him. That is the nature of miracles. Therefore, Lazarus could die again to put things back in their natural order. He died again so he could later be resurrected unto eternal life through faith.
What happens to all unbelievers? Do they all die a physical death? Yes. Will they be resurrected and judged? Yes. Since they are not resurrected unto eternal life to then be judged, they are simply resurrected, but not unto eternal life. Once they are judged guilty they will die a second physical death in the lake of fire (the second death). Therefore, Hebrews 9:27 only refers to the first physical death prior to judgment day.