Population Capacity Main Quest - problem

In the Population capacity Quest I see the Kings letter quest completed with a tick (I got 2 letters) the next part is 'complete the letter without addresser quest' this is highlighted green and with a tick but I haven't done this quest, have no idea what it was and the next part is locked! There is nothing in the sub folder (infact there is no subfolder):(

If you hover the mouse over the grayed quest, it should point out which requirements you need to fulfill for the quest to open it up, if you are not level 26 yet, that may be the reason.