Nostalrius Begins - Quality wow vanilla realm (1.12)

The quest A rouges deal is not being completed. I have fulfilled all of the objectives and when I go to the npc calvin montague he shows me the text that you get when you complete your quest but when I click complete quest the text just comes back again.
It let me clicks complete quest but it doesn't actually compete it, it just bring back the text.

Log out, close WoW, try deleting the WDB folder in your WoW Classic folder, then relog in and see if it lets you complete it.

If the above does not work, make sure you are not using any AddOns that will automatically complete quests for you. I had a similar issue and disabling the AddOn worked.