I'll assume you've done the things required to progress the quest:
Market Trading - purchase 300 stone from a town/city after the quest starts
Defending Your Homeland - built stone walls (playing Army v Town PvP will also work)
These quests have worked for most players so there might have been a bug that interfered with quest completion.
These sorts of bugs often resolve themselves when you restart the game.
I recommend restarting the game, attempting to complete these quests again (talking to Nothras after having done so) and if they still don't work exit the game then reply here with your log1.txt file attached before playing again (otherwise log1.txt will be overwritten) and we will investigate further.