Welcome to the Q&A Forum

Yes, asking and responding to questions is a paid feature. Unfortunately, this means you wouldn't be able to respond to old questions you have posted if you no longer have a paid subscription. You can, however, gain access to the Q&A forum without a paid account by getting over 500 MozPoints, which you can learn more about here. You can do that by adding valuable comments to the blog posts, completing your account profile, writing a blog post that gets accepted to the YouMoz blog, and a few other things noted in that link, as well.