Why is the Destiny 2: Armory Collection listed as Unavailable on the Epic Games Store?

The Armory Collection Pack contains items from both the 30th Anniversary Pack and the Forsaken Pack. If you own one of those packs, the Armory Collection Pack will show up as unavailable for purchase on the Epic Games Store. If you wish to purchase the rest of the contents from the pack, you may purchase the other pack you are missing (i.e. if you own the 30th Anniversary Pack you may purchase the Forsaken Pack and vice versa).

Note: You may also refer to Why is a game listed as Unavailable or not visible on the Epic Games Store? for more information regarding this.