Everytime I want to answer a question I need to fill CAPTCHA. I already answered 4 questions here and I also have account on other StackExchange sites. Does the system still think I'm not a human?
A CAPTCHA can be guaranteed if an A is prepared outside the sandbox (say Word or Notepad) and then copy/pasted in with "Post Your Question" clicked soon after.
Whether that is the cause for OP we can't be sure without further details (which I doubt will be forthcoming since OP seems not to have visited for eight+ months) so there seems little more to be said.
OP visited 17 days ago, so just seems not interested.