Ok, so I've searched the forum for an answer as well as google and I'm still stuck.

I took a break from Skyrim for a while and when I got back decided to finish the thieves guild quests.
So I've done all the main ones except for Under new management, and have finished the 4 city influence quests for Delvin.
I tried talking to Tonilia for the one about delivering Moon Sugar, but she won't give it.

I finished darkness returns and now nothing is happening.
Brynjolf keeps saying his ever famous phrase 'Sorry lad, I've got important things to do. We'll speak another time.'

Is there any way I can just finish this darn quest?
I've tried the suggestions out there; consoling, going to the middle of the cistern and waiting, talking to Brynjolf and then running out of the Ragged Flagon, nothing works.

I'm level 56 and really don't want to have wasted over 100 hrs just because I did the city influence quests after the main ones!