Trying to become the master of the thieves guild.

I have the Nightengale Armor and finished those quests (so I am thier leader). I have influence in Riften, Whiterun, Windhelm and Solitude.

I need to do five quests for Vex and Delvin in Markarth to gain the final city influence, but they never give me quests to go there. I'm level 23 in case there is a level limit or something. I keep getting quests for the other four cities and I've even tried refusing quests and grabbing new ones, but I never get one for Markarth.

In case it matters I have done the quests to give skooma to the Khajiit caravan also.

So what is stopping me from getting quests for Markarth?

Thanks.

Nothing. If you get a mission from Vex/Delvin, you can talk to whoever gave it to you straight after and reject it. So do that until you get two for Markath, head over there, do the jobs, and return. Rinse and repeat. I did this last night - took me two hours to do something like 14 radiant quests and two influence quests. Shouldn't take you too long.