Druhl
commented
5 years ago UPDATE:
Issue may just be visual (though confusing).
After handing in a different quest to this quest's completion NPC, a gold question mark appeared over the NPC. Clicking on it, this particular quest was still showing "grey" but did allow me to click on it through to quest completion. Note the on-screen quest tracker still displaying incorrectly.
ghost
https://www.wowhead.com/quest=9594/signs-of-the-legion
What should happen: Two types of mobs have a number killed requirement to advance and complete the quest.
What does happen: One of the two types (the Nazzivus Satyr - https://www.wowhead.com/npc=17337/nazzivus-satyr) increases the kill count (target is 8) when moused over and with on-screen announcement after each kill but in the quest tracker, count does not increase, and quest can not be handed in / completed.
My apologies, I should maybe have hidden the other quests in my tracker. At the bottom right you can see the mouseover box for the mob (showing 8/8) and a couple quest trackers above it, the one for this quest, incorrectly showing 0/8.