I agree with Steelish... post something in the roleplaying section and see if anyone bites there. You may have a better chance than the personals section. Either post a 'this is what I am looking for' and invite others to take part there or start off the scenario by describing the opening scenes and see who takes part.
Or is what you want an actual online play partner? Maybe you should consider seeing if any Doms out there have a desire for another sub who they want to be dominated by their existing sub?
Another thing, and this is from personal experience, you may find more success if you post more in other threads - contributing to the forums more by asking questions, answering other posts and so on. Going into the chatroom is also a good way to meet people, make friends and therefore get to know potential people to 'play' with. You can even set up a private chatroom in there to play with dominants in chat. A lot of people on this forum like to play with people they 'know' more intimately than just a personals post - seeing you as a person. It may help.