I have never successfully had a roleplay. I made the attempts, back in my peak Gaia days (2004-2007), but I think a lot of things got in the way. Sometimes it's just the usual; people post long and detailed character profiles then drop off from lack of interest. For me specifically, most of my attempts were to enter the communities of various breedable pet shops, which were often very cliquey. A lot of the more intense ones required a lot of thread participation, money to buy your pet, and a certain level of writing quality for an ongoing pet journal. I usually failed at at least two of those three things. I was also probably just very bad at RPing and bad at integrating into other peoples' social environments.
I never really got a lot of direct critique on what I was doing wrong. The one time I was given a reason for being passed over in an RP 'audition' to buy a pet, I was told my posts weren't long enough. To this day I'm not 100% sure what RPers expect for length. It feels wrong to write three paragraphs of internal narration and scene detail to pad out a single line of dialogue in response to what the other guy just said to you. It feels especially useless when I'm there to buy a pet. Why do you need a chapter about my character's dark past before you let me send you 5k gold for a picture of a dog?
I've had my best success in creating fun RP moments in places that don't RP, which probably says something about myself. I've been a part of other communities, usually forums, that had NOTHING to do with roleplay, and somehow gotten people wrapped up in building personal lore with me. So some of us would be families, and make up imaginary kids, or describe our super cool fortresses where we conduct raids on each other to steal each others' memes. I've done little games in art communities where one of my OCs will interact with other artists' OCs and then I draw the scene.
I think actually, since I'm primarily an artist and a writer (I make comics, in theory, when I get around to it...) part of my personal problem was that I want to tell my own stories. I even play MMOs like they're single-player games. I enjoy interactions, but I don't necessarily want to make collaborative works that way. If I really wanted it, I would have worked harder at getting good, instead of wandering off to do my own thing. What I actually want is to make a good story on my own, without input, then get peoples' reactions after the fact. I don't want to roleplay OC-to-OC, I want to make something that people will then make fan OCs for. I've considered opening up some kind of venue for people to talk to my OCs, like an askblog on tumblr or something like that, so I have a comfortable control of the input flow. But first, I have to present my OCs in a way that people take interest in. I better get back to making my comics...
But I really wish Gaia's deep archives were indexed right so that I could go in to my oldest, cringiest posts and reassess whether or not I really was just a bad RPer.