How do you practice romance scenes?

I am also having issues practicing the romance scene. There is no option for my sim to do so; I can click any other sim and the option shows up, but the action never takes place. They get into position, shake themselves like they are going to start, then the dreaded red slash sign appears above my sim and nothing happens. Over and over again. I have tried it in my home, on the street, in clubs, in bars, at the movie studio and with more than 20 sims. It did happen once when I was at a fund raiser with a sim who is a bff, but have no idea why it worked that time and why I can't seen to figure out how to make it work again. Please, any advice is helpful!!

I have also noticed that inviting co-stars and director to my home doesn't always work. The director almost always shows up, but the co-stars don't always come over, thus leaving my prep work undone. I have also tried the prep work once on the movie studio lot, but by then the prep work seems no longer awardable.