How to make romantic interactions work with enemies with benefits?

Watch out for embarassed and tense moodlets from bad conversations. From my experience even if the sim is overtly Very Flirty, as long as an Embarassed moodlet is buried somewhere, romantic and friendly socials tend to fail.

If you buy "Beguiling" from the Rewards store, you can easily set them in a very flirty mood by just using the "Beguile" interaction.

Also, I'm not sure if you checked or not, but maybe the target sim has a different gender preference than your sim

I made them both attracted to men.

I have a couple in a scenario where they have a red friendly bar and a red romantic bar, and have a bad sentiment to each other. I will have to try buying the beguiling trait when I can for each of them. Someone said you can initiate conversation with others and the other one can join in but don’t direct any questions at each other. I also read that they can watch tv together……. I haven’t tired it yet, but I think I will see if they can cloud gaze together without negative consequences.