Oh that's very weird. Usually whenever people receive this bug, this method fixes it. Does it happen even if you go back to a previous save and try again?
Hi! I'm having the same problem. I both reloaded an earlier save and tried starting a new game entirely without saving or reloading and the final action still remains locked. Might there be a way we can bypass this at all if this is a common bug that hinders progress? ;;
