Forum Discussion
Based on what I've seen so far, if those haven't already unlocked since the patch you may need to try reloading a save or playing through again if you don't have an earlier save game available, unfortunately.
I would try loading any save you have from ME1 after completing a romance there, if possible. Once that's loaded, save over it again so you'll now have a save file updated since the patch.
After that point try loading your ME2 save and completing the romance again there. You mentioned having one just before a Tali romance, so that may be the quickest to try.
Edit: Success, thanks for confirming that did the trick! 🙌
Does Paramour 2 even unlock if you "rekindle" your romance with Liara in ME2 LotSB?
I've tried before and after the patch. If the achievement doesn't unlock for rekindling your romance with Liara in ME2 they really should change the conditions of the Paramour 2 achievement to "Establish a Romance or Cheat on your Lover (but also don't bother romancing Samara or Kelly so if you're playing as FemShep STRAIGHT ROMANCES ONLY!)"
I don't mean to sound aggressive. I'm just trying to understand the logic if it's working as intended.