I don't know why but some of my tweets have a lock beside them and people can't retweet them. My accounts isn't on private and not all of my tweets have a lock icon. So how do I get rid of it?
If your account isn't set to private, but it's doing that, you'd be best contacting Twitter directly about it. You can open a support ticket here.
If you've only recently changed it to private, it might be one of two things, potentially: