The most common and reliable guide I have found for brokering peace between the geth and the quarian is the following:
In order to achieve peace between the two races, you need to get 5 to 7 points. These points are based on your ME2 and ME3 decisions. If you have 4 points or below, you cannot achieve peace.
-Rewrote the Heretics (0 points)
-Destroyed the Heretics (+2 points)
-Tali is NOT exiled (+2 points)
-Tali has been exiled/You did not do the Loyalty Mission (0 points)
-Resolved Legion/Tali conflict either using the Paragon or Renegade options (+1 point)
-N7 Mission: Save the Admiral on Rannoch in ME3 (+1 point)
-N7 Mission: Destroy Geth Squadron on Rannoch in ME3 (+1 point)
-Completed Legion's Mission in ME3 (or no peace)
Now, I imported an ME2 save where I destroyed the heretics(+2), Tali is exiled, I resolved the Tali/Legion conflict using a renegade option(+1), I saved the admiral on Rannoch(+1) and destroyed the geth squadron(+1). Of course I also did Legion's mission.
This gives me 5 points which is enough to get the option.
I know that I also need 4 bars of reputation...which I think I have. I have about 3.5 bars of renegade, then above this I have an additional bar of what I assume is paragon, as it has a harp symbol and is blue.
This should be 4.5 reputation in total.
From what I can tell I more than meet the options to successfully broker peace between the quarian and the geth, however, I don't even see the options. They are not greyed out; they don't appear at all.