Summed up in title. I got a second steam key finally after the first was seen as a duplicate key and it still sees this one as duplicate! Don’t know how many people are affected by this the second time around so thought I’d say something.
Got a third key and it worked. Seems like an active problem. Just wanted to let anyone know who also had this issue to keep refreshing your halo insider page to see if the key changed and try again.