You need to finish Cassie's route, and then something will have changed in the BDSM club!
Already finished her route, a long while ago... in fact, I didn't really do anything at the club at all until Cassie's route was finished. Personally, for some reason the bdsm club and its scenes just don't really interest me, and I'm not quite sure why, since I've loved the rest of the game's content, which is full of bdsm-related stuff all over the place. Thankfully, Ganonpunch seems to have already answered my question (thank you, Ganonpunch). Not too fond of this particular solution though, since I consider my presence at the club to be sorta just, a thing I'm doing for Fawn (I really do like her, she's a great character), and doing stuff with Arlene here strikes me as something that neither Fawn nor I would particularly like (Arlene, quite frankly, kinda scares me. The conclusion of the Cassie route quite firmly established Arlene to me as someone who... though mostly an ally, is definitely not a friend, and is generally someone to keep at arm's length). So, unlike almost everything else in the game so far, this solution strikes me as... just a thing I am doing to progress, rather than a thing I am doing because I want to.