My friend and I have completed all the steps for the "The Invitation" questline, but we are still unable to purchase tributes. They are all blacked out and when hovering over them, it says "Requires quest progress." After reading online it seems that the final step of the Invitation questline, following completion of the Menagerie (and looting of the chest) is to return to Werner, and loot a chest adjacent to him. Neither of us saw a chest after completing the questline, and we are unsure if this may be a bug.
Any help would be appreciated.
your post is confusing 2 quest lines. Tributes are part of the tribute hall quest/event. The menagerie is completely different. Both are called Invitation but do not have anything to do with one another.